Past Calls

PT-CERN Call 2022/1

Results

PT-CERN PhD Grants - Call 2022/1 - Candidates Final Classification - Particle and Astroparticle Physics and associated scientific domains

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-009 Giacomo Da Molin
ID-001 Esteban Chalbaud
ID-003 André Cordeiro
ID-016 João Viana
ID-020 Lucio Gibilisco
ID-017 Tiago Emanuel Anjo de Oliveira Custódio

Results
PT-CERN PhD Grants - Call 2022/1 - Candidates Final Classification - Technologies associated to the Portuguese participation at CERN and their transfer to society
There was only one candidate and she rejected the grant.

Results

Theses (29 theses registered)

Studying the origin of the elements with radioactive ions at ISOLDE/CERN
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Daniel Galaviz Redondo

Co-Supervisor: Francisco Javier Ferrer Fernández

Institution: FCUL (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The main goal of the present PhD program is the execution and analysis of experiment IS698 at the ISOLDE/CERN facility. By getting involved in all characteristic phases of the experiment, the PhD candidate will receive a complete eduation in experimental nuclear science at one of the world-reference facilities in the production and study of radioactive nuclei like the one located at CERN. By executing the various tasks depicted in the workplan, the PhD candidate will: - advance in the knowledge of nuclear instrumentation, by directly participating in the preparation and setup of the hardware and software components of the experiment. - develop data analysis skills, by analyzing the data obtained during the measurements at the ISOLDE/CERN facility. - improve programming skills related to particle transport simulation (use of GEANT4 framework), nuclear reaction modeling, and study the impact of the deduced nuclear properties in astrophysical reaction network calculations. - Present the result of the measurements in international conferences and publish them in peer-reviewed international journals. - Participate in an international collaboration, interacting with scientist from different laboratories and countries in Europe.
The partonic structure of hadrons
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Gernot Eichmann

Co-Supervisor: Alfred Stadler

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Almost all mass of visible matter rests in atomic nuclei and therefore in nucleons, which are complicated bound states of “partons”, namely quarks and gluons, the fundamental degrees of freedom in QCD. However, the structure of mesons and baryons is much more complicated than the naïve quark model suggests and their internal composition is still largely unknown territory. The distribution of quarks and gluons inside hadrons and nuclei, the decomposition of spin and orbital angular momentum, and the role of gluons in the dynamical generation of a hadron’s mass are all urgent questions that need to be answered. The experimental landscape in the forthcoming decades will be shaped by the COMPASS++/AMBER experiments at CERN and the Electron-Ion-Collider (EIC) at Brookhaven, which aim to map out the partonic structure of mesons, nucleons and nuclei and reveal the origin of the glue that binds their constituents. The central quantities of interest are parton correlation functions such as PDFs (Parton Distribution Functions), GPDs (Generalized Parton Distributions) and TMDs (Transverse Momentum Distributions), which encode the spatial and momentum distributions of partons and their spin and orbital angular momentum correlations inside hadrons. The goal of this project is to compute PDFs, GPDs and TMDs with nonperturbative continuum calculations by employing a new technique that has been recently established. This will deliver new insights on the internal structure of hadrons and provide much needed theory support for upcoming experiments at CERN and other facilities.
Signatures of gravitational waves in non-homogeneous cosmologies
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

So far, gravitational waves have mainly been described in the context of homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker (FLRW) models. A more general class of non-homogeneous Lemaître-Tolman-Bondi (LTB) models may be a more natural and observationally consistent alternative to the present homogeneous and isotropic paradigm. Predictions for gravitational waves from the early universe and from astrophysical sources are still missing for this class of models and are necessary for the preparation of the next ESA flagship missions for cosmology: LISA and Euclid. The main objective of this project is to develop the framework of GW generation in LTB, and build realistic simulations of the GW background based on it, using a combination of numerical and Machine Learning methodologies. The plan is to perform a detailed characterization of the properties of the GW signal that will be detected by future GW experiments for this class of models. We will also propose to explore the complementarity between GW and Electromagnetic (EM) surveys, combining information carriers in a multi-messenger approach, to identify cosmological signatures of LTB non-homogeneity in future datasets such as the forthcoming ESA/Euclid satellite data releases.
Modified Gravity theories: impact on cosmological observables and astrophysical implications.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: Noemi Frusciante

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

High precision cosmological probes seem to support the current standard cosmological model, ΛCDM. However, the most recent observations appear to reveal tensions between the theoretical predictions and observations. This provides the motivation to look beyond General Relativity (GR) in search for a fundamental theory of gravity. Modified Gravity theories (MG) attempt to solve these issues and minimise these tensions. With the advent of more precise cosmological probes, it’s worthy to explore the theoretical predictions and observational consequences of MG theories, to correctly interpret present and future data and thus filtering specific models. In this project, we propose to explore the fundamental nature of gravity by exploring several models of MG, namely interacting Dark Energy (DE), symmetric teleparallel gravity, higher dimension theories, and Horndeski models, by studying their phenomenology, cosmological and astrophysical implications in a model independent approach. This work will allow us to test the nature of gravity and provide tighter constraints on the models.
Visible gravitational echoes from invisible sectors
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Felipe Ferreira de Freitas

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

The recent Nobel prize winning detection of gravitational waves (GWs) [1] has opened up a new era of GW astronomy and, more generally, fundamental physics explorations. A potential observation of the stochastic background of primordial GWs may indicate possible New Physics (NP) beyond the SM (BSM) [2]. Indeed, such an observation may become a novel probe for New Physics possibly even inaccessible to traditional collider and astro-particle physics measurements. The principal purpose of this thesis is to explore the potential of future GW interferometers such as LISA, BBO, DECIGO and the EinsteinTelescope (ET) in probing NP scenarios that include both dark/hidden sectors as well as high-energy phase-transitions above that of the electroweak (EW) scale. As a guiding principle the work will be inspired in a class of recently proposed models [3,4] based on an Unification paradigm that includes the flavour structure observed in nature as a fundamental gauge interaction. The presence of larger symmetries in an energy range that goes from 10 TeV up to 1000 TeV and the need for a dark-sector to cancel gauge anomalies, the work will be focused in the production of multi-peaked primordial GWs covering the mHz-kHz frequency range.
Testing the WIMP paradigm to the limit
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rui Santos

Co-Supervisor: Milada Margarete Mühlleitner

Institution: FCUL (Universidade de Lisboa)

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

The search for Dark Matter (DM) is one of the main goals of present high energy physics and astrophysics experiments. Many direct and indirect detection experiments together with searches at the Large Hadron Collider (LHC) have so far provided only bounds on the DM mass and couplings. DM candidates, which may be bosons or fermions, arise in many extensions of the Standard Model (SM) in a wide mass range. In recent years there has a been a shift from the so-called Weakly Interacting Massive Particle (WIMP) paradigm to the very low mass region of axions and other very light particles. However, many of the present and future planned experiments for direct and indirect searches, such as e.g., the XENONnT [1], DARWIN [2] and SWGO [3] experiments, together with the high luminosity stage of the LHC and future colliders, will still be focused on the WIMP mass region. Furthermore, many of the simplest models one can build still allow for a WIMP candidate. Hence, even if no DM signal was found yet, we should certainly not rush into declaring the death of the WIMP with still so much to explore. The objective of this work is to test the WIMP paradigm to the limit - will future experiments finally gives us a WIMP, or will we have to find a new paradigm? Higher order corrections can change the limits obtained from the experiments for DM masses and couplings within each model. In some cases, higher order corrections have a dramatic effect on the interpretation of the results. More importantly, it is possible that corrections to similar processes can have a much higher impact in say indirect detection than in direct detection. Therefore, only corrections to all processes involving DM in the three probing modes: direct, indirect and collider, can give us a clear idea of their importance. We expect to give a significant contribution towards answering if we are definitely entering a very light/heavy era for DM or if the WIMP is just in a moribund condition until we finally detect it.
Applications of modified gravity in high energy astroparticle physics and cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

From the experimental side, General Relativity (GR) has been successfully tested directly in the Solar System in its weak-field, slow motion regime. Binary pulsars, most notably the Hulse-Taylor system PSR 1913 C 16, allow for indirect tests beyond the Solar System. However, strong gravity tests are still scarse and gravity is tested poorly at the scale of galaxies and clusters, where Newtonian gravity breaks . This has led to the development of several modified theories of gravity to replace galactic dark matter. In fact, the discovery that the present expansion of the universe appears to be accelerated indicates that gravity may not be described by GR at large scales. To explain the cosmic acceleration, one needs to introduce an exotic negative pressure fluid, denoted dark energy, which constitutes approximately 70% of the energy content of the universe. Dark energy is thus an ad hoc solution to the problem of the present acceleration of the universe, and alternatives such as modified gravity have been explored. In fact, a plethora of modifications of gravity have been proposed as reliable alternatives to dark matter and dark energy. In the high-energy astroparticle physics regime, modified gravity could shed light on several outstanding problems in particle physics, such as the nature of dark matter, since its thermal production in the early universe may give rise to a relic density of the same order of magnitude of the present dark matter density. Particularly relevant in these scenarios could be the role played by modified gravity, as these theories predict a thermal evolution of the universe different with respect to one based on GR. More precisely, modified gravity predicts a modification/amplification of the expansion rate of the universe with respect to standard cosmology so that the thermal relics decouple with larger relic abundances. Consequently, the correct value of the relic abundance comes out from larger annihilation cross-sections.
Heavy baryon excitations with functional calculations: confirming CERN discoveries and predicting new states
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Gernot Eichmann

Co-Supervisor: Teresa Peña

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Our understanding of heavy baryons has expanded considerably in recent years with the discovery of many new states including charm and bottom quarks at the LHC. It is crucial to develop a theoretical understanding of such states from first principles in Quantum Chromodynamics (QCD). The goal of this project is to compute the spectrum of heavy baryons using functional methods in QCD. These methods have been successfully employed in the light-baryon sector, and our aim is to extend them to charm and bottom baryons, as well as to computations of their excitations and electromagnetic form factors. An important open question concerns relativistic effects which are crucial for light baryons, but recent studies suggest that relativity could also play an important role for charm and even bottom baryons. We will also implement current progress in the calculation of QCD's n-point functions, a key improvement towards ab-initio calculations of heavy baryons.
Probing CP couplings in ttX production at the Run3 of the LHC.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio Onofre

Co-Supervisor: Ricardo Gonçalo

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

In this PhD thesis proposal, we explore CP discrimination, in the associated production of top-quark pairs with generic scalar/pseudo-scalar and vector/axial-vector boson mediators, at the LHC. In addition to the Higgs boson, which may reveal a non-Standard Model (SM) CP (charge-parity) nature of the couplings to heavy quarks, these searches are also looking for hints of Dark Matter (DM) candidates, in simplified models with spin-0 and spin-1 particles, that act as mediators. Events from the associated production (ttX, X=spin-0, spin-1) of top quarks are searched for in the single lepton and dilepton topologies, in proton-proton collisions at the Run3. Following full kinematic reconstruction, a search for specific angular distributions that are sensitive to the CP nature of the mediator couplings, not only to the magnitude of the mixing angle but also to its sign, is expected to be performed with the aim of discriminating, as well, the dominant backgrounds at the LHC from the signals under study. The mass range covered by the searches, focuses on the very low mass region up to masses O(TeV), using the Standard Model Higgs boson mass case, as a benchmark for the CP observables performance. The use of Machine Learning (ML) algorithms, for event classification, is also expected to be performed since it has shown to be particularly promising in the context of High Energy Physics (HEP). These algorithms will be tested in ttX associated production, with completely new coverage of the CP parameter space. The impact on the signal sensitivity is to be quantified in terms of cross-section measurements or 95% CL limits (in case no New Physics is discovered), using ATLAS data collected at the Run3. State-of-the-art Monte Carlo simulations like MadGraph5 with specific UFO models will be used. In addition, a global fit using ML algorithms will be performed to constrain the Wilson coefficients within the Standard Model Effective Field Theory (SMEFT).
Atomic inputs for probing the r-process in kilonovae
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Sampaio

Co-Supervisor: José Marques

Institution: FCUL (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

In this proposal we intend to make a relevant contribution to the questions "Where are the heaviest elements in nature produced? And can we identify an astrophysical signature of their production?". Recent studies of the evolution of light curves of kilonovae, and the observation of a kilonova electromagnetic transient associated with the gravitational wave signal GW170817 point to the production of r-process elements in neutron-star mergers.[1] In order to study such electromagnetic signals it is necessary to combine an accurate description of atomic parameters with sophisticated astrophysical simulations. However, atomic data regarding r-process ions, particularly lanthanide and actinide ions, are scarce. For that reason, in this work level energies, excitation/ionization cross-sections and oscillator strengths between individual levels will be calculated for all neutral and charge state lanthanide and actinide ions relevant in the density and temperature range found in the ejecta expansion in a kilonova. For this FAC and MCDFGME codes will be used, as they represent today the state of the art in atomic structure calculations. The results will serve as input for modeling the luminosity curves of kilonovas beyond the local thermal equilibrium (LTE) approximation. The PhD. research activities will be developed at LIP (Laboratório de Instrumentação e Física Experimental de Partículas), Lisbon, Portugal and at GSI (Helmholtz Centre for Heavy Ion Research), Darmstadt, Germany.
Machine Learning Methods to improve the Phase II ATLAS Trigger system
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Patricia Conde Muino

Co-Supervisor: Inês Ochoa

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The objective of this research project will focus on the improvement of the calorimeter clustering and jet reconstruction algorithms, using ML techniques, for the Phase II Upgrade of the ATLAS detector. The methods to explore include several possibilities, from the use of ML to improve the clusters or jets energy measurement to the exploration of Graph Neural Networks for the calorimeter clustering reconstruction.
Unravelling Physical Equations from Experimental Datasets using Symbolic Machine Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Our global objective is to help illuminate current tensions in Cosmological Models as well as find an “Unbiased Nature” of Dark Energy (DE), Dark Matter (DM) and hypothetical New Physics underlying within these "Terra Incognita" hypotheses. Indeed, we aim to find physical interpretations of formulae that our AI agents will yield through Symbolic Regression and other techniques, linking them with Fundamental Physics operating in the early Universe. To achieve the above, we will start by deriving underlying profiles of Dark Matter halos, voids and the Universe’s mean background density from modern astronomical survey data such as ESA’s Gaia and Euclid. Then, contrasting these models with predictions relying on untested assumptions about the Dark Universe and the Cosmological Principle. Through our own novel algorithms and heuristics leveraging Symbolic Regression and Machine/Deep Learning innovations emerging in the literature, we will infer data-driven equations and seek first model-dependent, then model-independent, information directly from Cosmological and High-Energy Physics (HEP) experimental data.
Testing the nature of light and ultralight dark matter with deep learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Felipe Ferreira de Freitas

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

This thesis proposes a synergy between the areas of strong gravity, cosmology and particle physics in order to explore the Dark Matter (DM) paradigm. The deep learning techniques necessary for these studies will be based on evolutionary optimization algorithms and computer vision methods recently developed both in the context of particle and gravitational wave identification. Contrary to the typical approach taken by the strong gravity community, this thesis aims at the construction of concrete particle physics models where ultralight DM particles can emerge either as pseudo-Nambu-Goldstone bosons or as vector bosons such that they can reveal themselves in the form of stable halos around compact astrophysical objects. However, such halos are only viable when the Compton wavelength of the field approximately matches the gravitational scale of the compact object. For the known astrophysical objects, such as black holes, whose mass ranges from 1-10¹⁰ solar masses, this means that such bosonic particles must have masses between 10⁻¹⁰-10⁻²⁰eV. The presence of an ultralight bosonic sector implies further bosonic particles that are not necessarily ultralight, and perhaps at the reach of the LHC if their mass is larger that 1 GeV. Furthermore, for models featuring neutrino mass generation mechanisms, a sterile neutrino can also become fermionic DM candidate with masses in the keV-MeV range. In this thesis, a catalog of models that can consistently predict light and ultralight bosons as well as sterile neutrinos will be constructed. These are extraordinary candidates to offer multi-component DM which will be studied and confronted with data both from the gravitational, collider, and direct detection channels.
Fundamental cosmology from precision spectroscopy: The ESPRESSO road to ANDES
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The observational evidence for the acceleration of the universe shows that canonical theories of gravitation, cosmology and particle physics are incomplete. The LambdaCDM model is a simple convenient approximation to a more fundamental theory, whose details or underlying principles are still unknown. Astrophysical facilities must search for, identify and characterise this new physics. My thesis will address this challenge, and specifically two questions: 1) Are the laws of physics universal? 2) What makes the universe accelerate? This relies on state-of-the-art high-resolution spectroscopy data from the ESPRESSO Guaranteed Time Observations, leading to the most accurate and precise such astrophysical tests, directly testing the Einstein Equivalence Principle and constraining dynamical dark energy. In parallel, I will participate in Phases B and C of construction of the ANDES spectrograph, specifically by optimizing its cosmology and fundamental physics science cases, including the exciting prospect of the detection of the Sandage test signal.
The many faces of the Next-to-minimal Two Higgs Doublet Model
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Pedro Ferreira

Co-Supervisor: António Morais

Institution: Universidade de Lisboa

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

This work focuses on the class of Next-to-minimal Two Higgs Double Models (NTHDM)and the exploration of their characteristics in the aspects of beyond the standard model(BSM) particles like dark matter (DM) candidates, new scalar particles, exotic neutrinos,lepto-quarks and their signature in flavor observables, colliders and the possibility of emerging gravitational waves (GW). The NTHDM provided a broad field of studies and recently, a list of possible anomaly-free implementations of three right-handed neutrinos and a type-I seesaw mechanism was introduced in [1]. We will perform a thorough examination of the NTHDM class of models and their different scenarios and test them in the Large Hadron Collider (LHC) Run 3, if we are interested in the phenomenology of BSM particles, or in gravitational wave observatories like LISA or the future Big-Bang-Observer and Einstein-Telescope that will probe energies from 1 to 104 TeV
Jetography in Heavy Ion Collisions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Liliana Apolinário

Co-Supervisor: José Guilherme Milhano

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Heavy-ion colliders provide ideal laboratories to explore Quantum Chromodynamics in extreme conditions, particularly the Quark-Gluon Plasma, a rapidly expanding, nearly perfect liquid that filled the early Universe. Due to its unique properties, it is the main object of study at ultra-relativistic heavy-ion colliders such as RHIC (BNL) and LHC (CERN). Jets – collimated sprays of hadrons with a common partonic origin – are produced concurrently with the collision. These objects traverse the extended medium, experiencing QGP-induced interactions (quenching), observed as modifications to jets’ initial energy and substructure. Spanning a wide range of scales, jets provide insight into QGP expansion. This proposal aims to study QGP evolution using jets, by extending current theoretical approaches to expanding media and constructing jet substructure observables sensitive to its time structure. This will provide constraints on existing hydrodynamical models and increased experimental control of heavy-ion data, essential steps towards a tomographic analysis of the medium.
New Physics and Vector Like Fermions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Joaquim Silva-Marcos

Co-Supervisor: Francisco Botella

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

The main focus of this thesis proposal will be on the development of models with vector-like fermions (VLFs), but multi-Higgs models shall also be explored. The topics to be covered are, amongst other, the development and use of (new) concrete tools to test physics beyond the SM and explore NP models which are consistent with the Electro Weak Precision Measurements (EWPM) of the current and of future data, coming from LHC or others. While developing these NP models we aim to achieve exciting and impactful predictions which may be able to point experimentalists to look for new exotic phenomena. We shall also focus on very sensitive CP violation measuring parameters such as ε_K, ε’/ε or others, which may pose strict restrictions to these models and their content. Additionally, in our analysis of models, we will use other powerful tools based on weak-basis invariants. We will look for alternative forms of generating the mixings and masses of the lighter quarks with the introduction of vector-like quarks (VLQs) and shall look for new possible sources of CP-violation in both the quark and lepton sector with VLFs. The CKM unitarity problem, is also an important problem which we will be addressed in the context of VLQs as well as the NP effects it entails (e.g. flavour changing neutral currents). Currently, one of the main issues at the LHC is the search for new heavy fermions, e.g. quarks with masses beyond the top quark, as is the case of a heavy-top and which occurs naturally in models with VLQs in the up sector, or in the case of the leptons, the search for heavy Majorana neutrinos. With this in mind, we will be studying predictions for processes, possibly, to be witnessed at the LHC, as e.g. the hypothetical decays of these new heavy fermions. Thus, a strong interaction with experimentalists at LIP/CERN will be required. The student will conduct research at both the Centro de Física Teórica de Partículas (Lisbon) and Instituto de Física Corpuscular (Valencia).
Anomaly detection in the search for new physics with the ATLAS detector
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Inês Ochoa

Co-Supervisor: Patricia Conde Muino

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

This project foresees the application of anomaly detection methods in the search for new physics in proton-proton collisions with the ATLAS detector at the Large Hadron Collider. ATLAS detector data in final states with high-energy jets will be analysed. The candidate will explore the new Run 3 dataset, to be collected starting in 2022, looking for signs of new resonances by taking advantage of state-of-the-art machine learning techniques for anomaly detection that can identify rare signals and distinguish them from background processes with cross-sections that are several orders of magnitude larger. Unsupervised and weakly supervised searches will be examined, with the aim of ensuring a robust and model-independent exploration of the dataset. The study and implementation of novel machine-learning methods for data-driven background estimation is also expected. The candidate will work with a team at LIP which has vast expertise in hadronic final states and that has led recent ATLAS publications in searches for new physics with these final states. The candidate is also expected to contribute to the successful operation of the experiment, in particular in the trigger and jet performance. The candidate is expected to develop their research alongside members of other institutions that are part of the ATLAS Collaboration and to travel to CERN to present their work.
Collapse or collide: improved analysis of black hole formation mechanisms
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Rocha

Co-Supervisor: David Hilditch

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

For several decades black holes have played a central role in theoretical physics, and the last few years revealed they are more than constructs of human imagination: we can actually observe them. In the context of general relativity (GR), we have a very good understanding of how black holes are formed under gravitational collapse. Furthermore, there are some indications about how black holes can result from high energy collisions. However, all (semi-)analytic studies of black hole formation processes are overly simplistic in the sense that they adopt, at best, perfect fluids to describe the matter involved. Additionally, this knowledge is mostly based on the assumption that gravity is describer exactly by GR, even at scales where we would naturally expect quantum gravity to take over. This project proposes to further develop the studies of gravitational collapse and shock wave collisions. Relativistic elastic bodies will be considered in gravitational collapse and the impact of the matter’s elasticity in critical collapse and high energy collisions will be assessed. In addition, we will also consider the effect of higher curvature corrections to GR on processes that yield measurable signatures of gravity. Such modifications to gravity are expected to leave imprints on critical collapse, since this subject deals with the formation of black holes at arbitrarily small scales. Gravitational collapse in the near critical regime is particularly relevant to understand the distribution of primordial black holes and to investigate the production of very massive hypothetical particles as products of Hawking radiation. The specific behavior of collapse and compact object formation is particularly relevant to understand the evolution of the universe and and the nature of dark matter. Thus, while the research program aims to improve our present knowledge concerning black hole formation, it has also important implications for beyond-standard model physics and cosmology.
Unified equation of state consistent with astrophysical, gravitational, high- and low- energy nuclear physics data and its applications
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ilidio Lopes

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The compact astrophysical objects, i.e. neutron stars (NSs), hybrid (HSs) and quark stars (QSs), are the densest physical objects accessible by direct observations. Moreover, the physical processes inside objects like HSs and QSs, for which is expected that matter goes through a phase transition from nuclear matter to a quark-gluon plasma, are equally poorly understood. This limitation comes from the fact that Quantum Chromodynamics and its lattice formulation have very limited applicability at large baryonic densities which cannot allow for obtaining a reliable equation of state (EoS). By imposing multi-messenger constraints from gravitational wave physics and astrophysics, e.g. LIGO/Virgo/KAGRA Collaboration, NICER, SKA, etc., detection of QS or HS can become another scientific breakthrough and prove the existence of quark matter. The PhD project is focused on modeling the properties of HSs, probing the properties of phase transitions and the EoS of strongly interacting matter at high densities.
Reaching for PeVatrons with the future Southern Wide-field Gamma-ray Observatory
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Mário Pimenta

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

This thesis focuses on measuring PeVatrons with the future Southern Wide-field Gamma-ray Observatory (SWGO), which will have the ability to survey the Galactic center. The recent observation of Galatic PeVatrons by LHAASO shows that it is possible to detect them provided that the experiment covers sufficiently large areas and has excellent capabilities of identifying the gamma-induced shower events amongst the hadronic background, as done in LHAASO at the cost of buried muon detectors. To find a cost-effective solution for SWGO that allows reaching for larger array areas with an excellent gamma/hadron discrimination, the following strategy will be employed: - Investigation of the characteristics of PeV electromagnetic and hadronically induced showers to identify quantities that might ensure a very high level of hadronic background rejection. For instance, the quantification of the azimuthal non-uniformities of the particle distributions on ground, that we introduced recently, will be fully explored with simulated and real data from LHAASO and Auger. - Development of dedicated analyses to estimate the muon content in air showers on an event-by-event basis, without shielding the detectors to absorb the electromagnetic component of the shower. - Optimization of the detector unit, making it as simple/cheap as possible. Namely, the use of only one PMT per station in the outer regions of the array will be studied. - Optimization of the array layout configuration. Such shall be done recurring to genetic algorithms to probe a more extensive phase space with a limited number of simulations. All these tasks are intertwined and should be iterated upon each other. Ultimately, the sensitivity of SWGO to PeVatrons and its physics reach should be investigated. The study on the shower characteristics will also be used to improve the determination of the cosmic ray mass composition and hadronic interaction properties, which might shed some light on the EAS muon puzzle.
Higgs and Flavour Beyond the Standard Model
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Gustavo Castelo Branco

Co-Supervisor: Margarida Nesbitt Rebelo

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

The proposed work plan aims at giving a contribution towards uncovering what is the Physics Beyond the Standard Model (BSM) in the Higgs and Flavour sector of Particle Physics. These two sectors are intimately related from the theoretical point of view. The connection is established directly at the Lagrangian level. In the state of the art it is explained why physics BSM is required. Symmetries increase predictability and will play a fundamental role in this work. Multi-Higgs models and models with an extended quark and leptonic sector will be considered. The work will focus on the origin of fermion masses and mixing, on analysing how to suppress dangerous flavour changing neutral currents and on the study of new sources of CP violation. In some extensions good dark matter candidates will arise. At all stages, the most recent experimental results will play a fundamental role in guiding the theoretical research.
Origin of the Arrow of Time in the Universe
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Marina Cortês

Co-Supervisor: Andrew Liddle

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

We always remember the past, never the future. This time asymmetry is universal: from Earth up to cosmological scales. We receive light that galaxies emitted long ago but never light they emitted in the future. Physics laws usually avoid reflecting this asymmetry, working in the same way whether time is increasing or decreasing. Therefore, we attribute the cosmological arrow of time to very specific initial conditions after the Big Bang, whose probability is around exp(10^(-90)) or less. Why the universe started in such an unlikely state is an unanswered question in Cosmology. In this work I will investigate whether the time asymmetry may already be present in fundamental laws, avoiding such very special initial conditions. My goal is to study time symmetry as an emergent phenomenon and provide a new perspective of different scenarios such as black holes, entropy, and quantum gravity; then support my results with numerical simulations.
IDENTIFYING SIGNATURES OF HYBRID STARS
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: TUHIN MALIK

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

In recent years, observational capacities have increased enormously. Strong constraints were set on the equation of state (EOS) of dense matter combining the discovery of massive neutron stars (NS) with the results obtained by the LIGO-Virgo gravitational wave (GW) observations of NS mergers and from X-ray observations of pulsars, with the NICER mission. NSs are one of the most interesting laboratories of the Universe, allowing us to study aspects of fundamental physics unreachable otherwise. NS observations will allow us to determine the stellar matter EOS. A second problem is the determination of its constitution since similar EOS may describe different scenarios. The project will answer the question “is deconfined quark matter present in the NS core?”, by studying possible signatures of quark matter. Rotating and non-rotation hybrid star properties will be calculated from hybrid star EOS based on microscopic models. Statistical methods will be applied to distinguish different scenarios.
The early universe as a window to particle physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rui Santos

Co-Supervisor: Milada Margarete Mühlleitner

Institution: FCUL (Universidade de Lisboa)

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

The Large Hadron Collider (LHC) will soon start its third run at a center-of-mass energy of about 14 TeV. A myriad of models has been proposed and searches at the LHC will try to cover as much parameter space of each model as possible. Many of these models also solve the most important outstanding issues of the Standard Model: provide a Dark Matter candidate and reproduce the correct matter anti-matter asymmetry in the universe. Hence, the complementarity with experiments from cosmology, astrophysics and astronomy can be used. The main focus of this work is to study phase transitions in the early universe together with gravitational wave experiments and the baryon number asymmetry as a guide to restrict the parameter space of models and thus find hints that can point us in the right direction both at the LHC and at future colliders.
Challenging Lambda with Euclid and beyond
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The growing amount of observational evidence for the recent acceleration of the universe unambiguously demonstrates that canonical theories of cosmology and particle physics are incomplete (if not incorrect) and that new physics is out there, waiting to be discovered. The most fundamental task for the next generation of astrophysical facilities is therefore to search for, identify and ultimately characterise this new physics. The acceleration is seemingly due to a dark component whose low-redshift gravitational behaviour is very similar to that of a cosmological constant. However, currently available data provides very little information about the high-redshift behaviour of this dark sector or its interactions with the rest of the degrees of freedom in the model. It is becoming increasingly clear that tackling the dark energy enigma will entail significantly extending the redshift range where its behaviour can be accurately mapped. A new generation of ESA and ESO facilities, such as Euclid, the ELT, and the SKAO have dark energy characterization as a key science driver, and in addition to significantly increasing the range and sensitivity of current observational probes will allow for entirely new tests. The goal of this thesis will be to carry out a systematic exploration of the landscape of physically viable dark energy paradigms and provide optimal discriminating observational tests. The work will initially focus on Euclid (whose launch is fast approaching) and will gradually broaden to explore synergies and probe combination with the SKAO and ANDES. The work will be done in the framework of the Euclid TWG, and the student will be a member of Euclid. This is a fundamental physics research project, using cutting-edge astrophysical facilities to probe the fundamental constituents and laws of the universe at length, time and energy scales that complement those that can be probed at cutting-edge particle accelerators.
The Effects of Dark Matter on Hybrid Stars and Their Thermal Evolution
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ilidio Lopes

Co-Supervisor: Violetta Sagun

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The recent detection of binary neutron star (NSs) mergers opened the possibility to study their internal structure and equations of state of matter at supranuclear densities through the gravitational waves emitted during their coalescence. On the other hand, compact stars may accumulate a sizable amount of dark matter (DM) in their interior. Recent studies have shown that DM is able to significantly impact hadronic matter properties in the stellar interior. However, this seems to be an oversimplifying assumption, as in the core of compact stars matter could go through a phase transition from nuclear matter to a plasma of strongly interacting quarks, dubbed hybrid stars. Thus, the present PhD project is focused on a study of the impact of DM on the properties of hybrid stars, their evolution, stability against radial and non-radial oscillations as well as observational signals of the presence of quark-gluon plasma in the stellar core.
Equation of state of hot non-homogeneous neutron star matter
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Helena Pais

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

Light nuclear clusters are expected to be ubiquitously present in astrophysical environments and play an important role in different astrophysical phenomena involving ultra-dense baryonic matter, but the estimation of their abundance demands to correctly estimate the in-medium modification of their binding energy. This can be achieved in a phenomenological way, if theoretical models are calibrated to experimental data from heavy-ion collisions in the Fermi energy regime, where these same clusters are produced in comparable density and temperature conditions. The present project aims at building a calibrated low density equation of state via a direct collaboration between theory and experiment . A Bayesian inference (BI) approach will be applied within a relativistic mean field formalism to build a set of equations constrained by observations and experiments for the whole range of densities of interest. A complete equation of state (EoS) appropriate to describe hot neutron stars will be built and made available.
Top quark physics and search for physics beyond the Standard Model at the Large Hadron Collider
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Joao Varela

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Motivated by the deviations observed in rare semi-leptonic decays of B mesons, the subject of the thesis is the study of lepton flavour universality (LFU) in top quark events produced in proton-proton collisions at the LHC. The LFU measurement is performed in the leptonic decays of W bosons in top quark events, including electrons, muons and taus. Measurements in this channel can be significantly improved by using advanced Machine learning techniques in the separation of signal and background events and by exploiting the large amount of data: the ones currently available, approximately 150/fb from Run1+Run2, will be reinforced by the upcoming Run3, providing additional 300/fb. The thesis, placed in the context of the Portuguese participation in the CMS experiment at the LHC, is integrated in the activities of the “Top quark” working group, and it is strongly linked to the Beyond the Standard Model searches within the CMS experiment.

PT-CERN Call 2022/2

Results

PT-CERN PhD Grants - Call 2022/2 - Candidates Final Classification - Technologies associated to the Portuguese participation at CERN and their transfer to society
According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-014 Pedro Martim Duarte Rosado

Results
PT-CERN PhD Grants - Call 2022/2 - Candidates Final Classification - Particle and Astroparticle Physics and associated scientific domains

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-015   José Bastos
ID-017    Kai Jenkins
ID-008   Christoph Gartlein
ID-023   Nuno Gonçalo Portela Branco
ID-040   Carlos Bruno Dias Fernandes
ID-028   Nuno Olavo Madureira
ID-003    Vinicius Luiz Barbosa Oliveira
ID-030 Matteo Turco

Results

Theses (34 theses registered)

Origin of the arrow of time of the Universe
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Marina Cortês

Co-Supervisor: Andrew Liddle

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The Energetic Causal Set [1] (ECS) model and it's quantum counterpart [2] were pioneered by one of the current supervisors, Marina Cortês, along with Lee Smolin, in the work which won first place in the inaugural Buchalter Cosmology Prize (2014). They introduced a model for the development of space-time that is intrinsically time-asymmetric throughout the emergence of space-time. The model was however implemented in only one spatial dimension. The current masters project [3] of the student candidate for this project, Vasco Gil Gomes, under the supervision of Cortês and Liddle, extended this to two spatial dimensions successfully replicating the 1d+1 results even though there were no a priori reasons to believe such an extension would be possible. The ECS framework allows the emergence of space-time from irreversible time dynamics, and simulations on 1d+1 ECS models have been shown to lead to emergence of time reversibility [1]. In ECS models new events are created through particle collisions with reversibility tied to emergence of dynamical limit cycles [4]. To ensure collisions in 2d+1 dimensions particles have been assigned a 2d finite cross-section measure. New collisions (events) are selected via a rule that seeks to extremize the distinctions between causal past sets of events. The extension to multi-dimensions which was the largest obstacle in the development of ECS for the past decade. I was able to use algorithmic information theory to solve the numerical challenges successfully replicating the 1d+1 classical results. In this Ph.D. project, I will first extend my ECS simulations to 3+1D, and carry out an extensive parameter-space investigation of both the 2+1D and 3+1D cases, statistically quantifying the transition to emergent time reversibility. The classical version will then be linked to the Hamiltonian formulation of time-asymmetric gravity, while a quantum completion will be studied using the two state vector formalism.
Unified equation of state consistent with astrophysical, gravitational, high- and low- energy nuclear physics data and its applications
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ilidio Lopes

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The compact astrophysical objects, i.e. neutron stars (NSs), hybrid (HSs) and quark stars (QSs), are the densest physical objects accessible by direct observations. Moreover, the physical processes inside objects like HSs and QSs, for which is expected that matter goes through a phase transition from nuclear matter to a quark-gluon plasma, are equally poorly understood. This limitation comes from the fact that Quantum Chromodynamics and its lattice formulation have very limited applicability at large baryonic densities which cannot allow for obtaining a reliable equation of state (EoS). By imposing multi-messenger constraints from gravitational wave physics and astrophysics, e.g. LIGO/Virgo/KAGRA Collaboration, NICER, SKA, etc., detection of QS or HS can become another scientific breakthrough and prove the existence of quark matter. The PhD project is focused on modeling the properties of HSs, probing the properties of phase transitions and the EoS of strongly interacting matter at high densities.
Exploring conformal bootstrap at higher points
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Miguel Costa

Co-Supervisor: Vasco David Fonseca Gonçalves

Institution: Universidade do Porto

Host Institution: CF-UM-UP - Centro de Física das Universidades do Minho e do Porto

Abstract

Quantum field theory(QFT) is quintessential to describe diverse physical phenomena spanning from condensed matter systems to particle collisions in high energy accelerators. Even more, it is one of our best hopes to unify quantum theory with gravity, with the Anti de Sitter/conformal field theory (AdS/CFT) duality being one of the prime examples where this is possible. However an important part of physical systems have a strongly coupled nature and thus evade most of the theoretical methods to tackle these problems. For instance, there is no good theoretical method to describe confinement or the existence of a mass gap. Advances in these questions, even if in toy models, would have a significant impact in theoretical physics. Fortunately, there has been progress during the last decades to develop and explore new non-perturbative approaches to describe quantum field theories at finite coupling. One of them is based on the old idea of deriving constraints from imposing consistency conditions based on the symmetries of the underlying theories. This is the essence of the by now famed conformal and S-matrix bootstrap programs. An important problem that only recently has become more tractable to bootstrap methods is the understanding of the structure of higher point functions in conformal field theories. The aim of this project is to explore the consistency conditions imposed by symmetry on these more complex objects. This is an ambitious program with implications for quantum gravity, CFTs and also QFT’s in general.
Probing the primordial quark gluon plasma with heavy flavour
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Yen-Jie Lee

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At the LHC, droplets of Quark Gluon Plasma (QGP) are created in Relativistic Heavy Ion Collisions. This exotic medium, named after its constituent particles, forms only under the uttermost conditions of temperature and baryon density. It is a state of quark matter predicted from Quantum Chromodynamics (QCD) as a consequence of the asymptotic freedom that colour charges manifest at high energies. As soon as the right conditions cease, this hot, dense, electrically and coloured-charged medium quickly harmonizes, giving rise to bound states like mesons and baryons. Nonetheless, exotic bound states like glueballs, tetra-quarks and so on are expected to form out of this rich environment. Hence, when a QGP droplet forms, it leaves a robust signature in particle detectors in terms of particle production, allowing its detailed study. All quark matter states can be sketched in the QCD phase diagram, which currently is still very unclear. Conducting QGP-related studies directly contributes to its mapping by examining the frontier where chiral symmetry breaks and hadronization takes place. Besides modern-day particle accelerators, QGP is associated only with extreme phenomena such as the vicinity of black holes, the core of neutron stars or even the quark epoch taking place right after the Big Bang. Thus, studies on the QGP are a window to the non-perturbative region of QCD but also to cosmology. A novel approach to studying the QGP is to explore heavy flavour states, now possible with the CMS detector at the LHC. More specifically, by exploring fully reconstructed b-hadrons, novel probes of the QGP that are achieved for the first time in nuclear collisions. This project aims at improving our understanding of quark hadronization, flavour and mass dependence of parton energy loss, and the underlying QCD mechanisms in the hot primordial medium.
Enhancing liquid xenon detectors for future experiments
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Alexandre Lindote

Co-Supervisor: Henrique Araujo

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Two-phase (liquid/gas) xenon time projection chambers (TPCs) lead the search for dark matter (DM) particles with masses between ~1 GeV and ~10 TeV typical of new physics at the electroweak scale. This is a well established and scalable technology, having evolved from detectors with a few kg nearly two decades ago to the current 2nd generation (G2) multi-tonne detectors (LZ and XENONnT). Nevertheless, there is broad consensus in the community that a larger (G3) detector is needed to probe the remaining WIMP parameter space down to the irreducible neutrino “fog” and explore other models motivating lighter particles. The XLZD consortium was recently formed by merging members from the XENON, LZ, and DARWIN collaborations, with the goal of designing and performing the required R&D towards such a detector. With 50-100 tonnes of xenon, it will be operating around the end of the decade and will serve as a Global Rare Event Observatory, with leading sensitivity to multiple DM candidates and, given its extremely low background, it will be able to competitively search for other rare physics phenomena – including 0𝝂ββ decay. This project foresees the integration of the student in the XLZD consortium, and an ambitious set of R&D activities to improve the performance of xenon TPCs in the search for 0𝝂ββ decay in Xe-136. The main goal is to achieve a position resolution of the order of ~100 µm at the decay Q-value (~2.5 MeV) by using a densely packed array of silicon photomultipliers (SiPMs), doping the xenon with H2 and D2 and optimising the geometry of the electrode grids. This opens the possibility of reconstructing electron track topologies and exploring the unique signature of this decay compared with the main backgrounds. The ambition is to take the Xe-136 0𝜈𝛽𝛽 half-life sensitivity of a G3 detector over the 10^28 yr level even using natural xenon, completely excluding the inverted hierarchy scenario and significantly increasing the possibility of observing this decay.
Charting QCD jet evolution in extreme conditions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Liliana Apolinário

Co-Supervisor: José Guilherme Milhano

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

This PhD program aims for a deeper understanding of the QCD building blocks across the different energy and density regimes and consistent QCD description ranging from perturbative to non-perturbative momentum scales. This will be done through the use of jets - spray of particles originated by the fragmentation of a high energy quark or gluon. These objects, massively created in current ultra-relativistic heavy-ion collisions performed at the LHC and RHIC, are the perfect laboratory for such studies. They hold in their substructure the effects of a multitude of QCD processes, ranging from the high-momentum perturbative emissions to the low-momentum, the non-perturbative phenomena such as the poorly known hadronization mechanisms that are responsible for confining partons at lower energy scales. In vacuum collisions, particle evolution can be understood via a momentum scale prescription that has been recently used to signal a transition between perturbative and non-perturbative QCD. Moreover, in heavy-ion collisions, the emergence of a strongly coupled QCD fluid, the Quark-Gluon Plasma (QGP), modifies QCD jets with the introduction of additional perturbative and non-perturbative effects. They also provide the unique opportunity of assigning a time prescription to QCD dynamics as the QCD medium dilutes simultaneously with the jet evolution. The purpose of this PhD is to achieve a consistent description of QCD processes by designing novel time-differential jet substructure observables, with different sensitivities to perturbative and non-perturbative momentum scales, successively complementing vacuum and heavy-ion studies with the insights from each collision system. Novel phenomenological approaches will be sought in a framework for a scale-differential study of fundamental physics. Altogether, this PhD’s output will provide the basis to quantify hadronization scales and QGP evolution through QCD jet probes.
Cosmic-ray isotopic composition measurements with the Alpha Magnetic Spectrometer on the International Space Station
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Fernando Barao

Co-Supervisor: Mercedes Paniccia

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

LIP has been part of the AMS collaboration since 1997, having actively partici- pated in the development and exploitation of phase 1 and 2 magnetic spectrome- ters deployed on the space shuttle Discovery in 1998 and on the international space station since 2011, respectively. The huge amount of data accumulated by the AMS experiment allows the study of the isotopes present in cosmic rays, of different nuclei and some presenting low fractions. Their secondary origin, as a result of the inelastic interaction of primary cosmic rays with interstellar matter, contributes to the study of cosmic ray propagation in the galaxy. In this thesis we propose to study the isotopes of hydrogen (Z=1) and boron (Z=5) nuclei, up to a kinetic energy per nucleon of about 10 Gev/n. The results envisaged in the thesis will greatly improve current measurements. Moreover, they will allow the study of their temporal variability at different times of solar activity and their correlation with it.
Machine Learning and Measurements of Higgs boson properties
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Pietro Vischia

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CERN Experimental Physics Department

Abstract

The main goal of the research program is to analyze the data and search for the production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons. The use of Advanced Analysis tools, such as Machine Learning and Deep Neural Network, will be pursued to enhance the sensitivity of the study. With the large data samples collected in Run2 and those expected to be collected in Run3 and beyond, the tools will be used to better understand the data and extend the sensitivity to Higgs searches to regions so far unexplored. The research will be carried out in the context of the Portuguese participation in the CMS experiment at the LHC, in the framework of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”. The candidate is expected to work in a team with a group of researchers. A strong motivation and a keen curiosity are essential requirements.
Spacetime and particle dynamics in Energetic Causal Sets.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Marina Cortês

Co-Supervisor: Andrew Liddle

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

We devote this project to fundamental issues of Physics inspired by progress in Quantum Gravity. Exploiting Sorkin’s causal sets approach [1; 2] and its award-winning development as Energetic Causal Sets by project supervisor Cortês and Smolin [3], I will study the structure of spacetime and its connection to time irreversibility, the emergence of Lorentzian manifolds and QFT dynamics on these spaces, cosmological signatures, and the nature of entropy. I will extend and enhance the simulations in [3; 4] to a more realistic 3+1D model, including Lorentz covariance and a cross-section for causal links. Supervisors Cortês and Liddle have already worked on the 2+1D case with encouraging results. These simulations will clarify the mechanism of transition from micro to macro causal structures and between reversible and irreversible regimes. The micro and macro causal structures need not agree in the causal sets approach. This dissonance is called disordered causality, and inspires us to quantise the causal structure using the Two Vector State Formalism [5; 6; 7]. Lorentzian manifolds can emerge from causal structures [8; 9; 10; 11]. We will exploit this possibility to retrieve the time-asymmetric extension of GR proposed by Cortês et al. [12; 13] by means of Cartan’s tetrad formulation of GR which allows to match the emergent flat spacetime to a curved manifold. Gravitational wave propagation is a promising observational test of this setup. Causal structures and entropy are profoundly connected [2; 14; 15]. We analyze this relation and work out astrophysical and cosmological scenarios. In particular, we will examine black hole entropy and the Bekenstein formula, and reinterpret the information and firewall paradoxes. Finally, the dynamics of vector and spinor fields in causal sets are yet to be determined. I will investigate them building the action for the electromagnetic field and coupling it to complex scalar and spinor fields.
Galactic Dust Environments - Attenuation Laws and their Effect on the Cosmological Distance Ladder
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Santiago Gonzalez-Gaitan

Co-Supervisor: Ana Mourão

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The Hubble tension, that is, the discrepancy between early and late Universe measurements of the Hubble constant, is one of the main topics of contention in modern cosmology. It is not known whether this tension is a product of new physics as of yet unaccounted for in the LCDM and Standard models or of systematic errors in the measurements. One of these potential systematics is dust reddening, which affects the color-luminosity relation of transients such as Cepheids and Supernovae, routinely used as standard candles in the cosmological distance ladder. Current dust corrections can be overly simplistic, assuming a common reddening effect for all transients and not differentiating between intrinsic and extrinsic color effects. This approach is flawed, as it has been shown that dust properties vary greatly across different galaxies and lines of sight. However, the exact root of these changes is still not fully accounted for. The goal of this PhD thesis is to provide a comprehensive study of dust reddening for transients and their host galaxies, examining often overlooked factors such as galaxy morphology/orientation, correlations with other stellar properties and varying dust screens in local galactic sub-structures. We will look at photometry and integral field spectroscopy for a variety of leading edge surveys, as well as perform extensive simulations of dust mediums in different galaxy types. Using statistical and machine learning methods, the relevant dust properties will be mapped and examined, in an effort to fully characterize the physical effects responsible for the variation of dust properties across the Universe. With this data, we will constrain the dust correction of transients, striving toward a distance ladder calibration with as few systematics as possible. This in-depth study of one of the possible sources of the Hubble tension will therefore provide unprecedented insight into the nature of its origins, potentially opening the doors to new physics.
Emergence of collectivity in QCD
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Co-Supervisor: Korinna Zapp

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The key signature of Heavy ion Collisions is the formation of a complex, hot and dense state of matter, referred to as the Quark-Gluon Plasma (QGP). Crucially, the QGP, in the first instances after the collision occurs, is in a stage of non-equilibrium, evolving from there to a medium which flows collectively and accordingly with the laws of relativistic hydrodynamics. The question of how the QGP comes into being, from the simple interaction rules in QCD remains a challenge. A path to be explored to answer this question is by looking at “jet quenching” phenomena, where jets’ sub-structure properties are altered, resulting from their interaction with the medium they transverse. After all, both the jet and the medium response it induces, will be in an out-of-equilibrium state, and so will experience a process of thermalization with the medium. The focus of this work will be the recoiling medium partons, as they will most likely end up being reconstructed with the original jet, turning the jet into a laboratory associated with partons which are at a wide range of thermalization scales. The main objective of this PhD thesis is therefore to use the dynamics of such perturbations as a pathway to understand the emergence of collectivity in QCD. To achieve that, an effective kinetic theory model, which has the great advantage of being valid in- and out-of-equilibrium, will be used and numerically incorporated into a MC event generator (e.g. JEWEL) to describe the distribution of the recoiling partons. Afterwards, a search for jet observables sensitive to the kinetic description of the response’s evolution will be conducted, in the hopes of opening up a door into a first principle understanding of the emergence of collectivity in QCD. Moreover, my work will aim to produce open access computational tools to be used to extract relevant information from LHC data on heavy-ion collisions.
Antenna parton showers in an expanding QGP
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Co-Supervisor: Liliana Apolinário

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At very high energies or densities, quarks and gluons produce a new state of matter known as Quark-Gluon Plasma (QGP) which is observed in heavy-ion collisions at modern colliders. Once produced, the QGP expands and cools very rapidly converting into normal hadronic matter. The very short lifetime of the QGP, of around 30 yoctoseconds, requires that all probes used to study the dynamics of the QGP have to have been produced concurrently with it. Jets, the offspring of energetic quarks and gluons produced in the collision, are the most versatile probes to understand the inner workings of the QGP. For realistic comparisons with experimental data, analytical calculations are complemented by simulation codes. Parton showers, the simulation of jet development, in the presence of a QGP have been developed over the last couple of decades. At present, no available parton shower encodes the wealth of theoretical knowledge we have achieved over the last few years. In particular, both the known modifications of colour coherence effected by the QGP on the parton shower and an explicit coupling of the interaction of quarks and gluons with the dynamics of QGP expansion remain to be formulated in the probabilistic framework of a parton shower. This project is expected to attain the probabilistic formulation of both effects and their computational implementation, for later implementation within an existing Monte Carlo event generator. This project is expected to have a lasting impact in maximizing the potential of LHC data. The work will be carried out in LIP-Lisboa and at Lund University (Sweden) under the supervision of Guilherme Milhano and co-supervision of Liliana Apolinário (LIP) and Korinna Zapp (Lund).
Applying Fractional Calculus in Cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Paulo Moniz

Co-Supervisor: Seyed Meraj M. Rasouli

Institution: Universidade da Beira Interior

Host Institution: CMA-UBI – Centro de Matemática e Aplicações

Abstract

The research that will eventually be conducted to write a PhD thesis within this proposal involves using a seldom used mathematical technique in high energy physics, but only because the HEP community has not been aware. Otherwise, it has been employed in many domains of physics: e.g. including fractional calculus in atomic or solid-state physics. The possibilities are pretty interesting as far as gravitational settings are concerned. In this proposal, we will investigate (analytically as well as numerically) fractional differential calculus and subsequent equations that generalize well-known frameworks in gravitational physics. We aim to consider the equations governing early universe either classically or from a quantum (semi-classically) perspective with several fractional derivatives. This may allow making predictions and contrast them to establish which limits or ranges for the fractional derivatives are permitted, given known gravitational data. Fractional quantum gravity is very much in its infancy, and many cases need to be investigated. Please note that, e.g. fractional uses of entropy and similar observables have found a correspondence in Barrow's proposals of entropy as fractal regions within suitable choices of parameters. Moreover, many models can still be established in the classical regime, which may have the ability to overcome the problems associated with standard counterparts. Can it be those gravitational physics, if using fractional calculus, even as phenomenological toy models will provide exciting and intriguing additional questions to address? Such a line is the course of the PhD research program.
Audible gravitational waves echoes from invisible sectors
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Vedran Brdar

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

The recent Nobel prize awarded detection of gravitational waves (GWs) [1] has opened up a new era of GW astronomy and, more generally, fundamental physics explorations. A potential observation of the stochastic background of primordial GWs may indicate possible New Physics (NP) beyond the SM (BSM) [2]. Indeed, such an observation may unravel NP that appears inaccessible to traditional collider and astroparticle physics measurements. This project aims to explore the potential of future GW interferometers such as LISA, BBO, DECIGO, Einstein Telescope (ET), and Cosmic Explorer (CE) in probing NP scenarios that include both electroweak (EW) scale as well as higher-energy phase transitions. The goal is to develop a (so far lacking) general-purpose and modular computational suite to automatize the calculation of the primordial GW (pGW) spectrum for generic BSM theories. While such tools will be valuable to the community, we will make use of those to study concrete physics cases, in particular, this will be applied in three classes of models: 1) minimal extensions of the SM in terms of the number of new particles, symmetries, etc. (e.g. classical scale invariance [25,26]); 2) extensions of the SM scalar sector with higher dimensional operators encoding unknown NP effects [11,30]; 3) GUT-inspired scenarios. While not exclusive, one will consider as guiding principle scenarios inspired by a recently proposed framework [3,4], based on a Unification paradigm where the family replication observed in nature emerges from a fundamental gauge interaction. With new symmetries present in an energy range from the TeV scale up to 10 PeV, this project will focus on the production of pGW covering the mHz-kHz frequency range, which is precisely the region where the aforementioned experiments operate.
New theoretical approaches in the context of LHC: increasing precision with 4-dimensional regularization methods
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Brigitte Hiller

Co-Supervisor: Adriano Cherchiglia

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

Computation of Feynman amplitudes involves the emergence of divergences in the loop integrals. As a consequence it is necessary the development of regularization and renormalization techniques that allow for a consistent treatment and removal of these divergences in a simple way. Implicit Regularization (IReg) is a regularization scheme that operates on the physical dimension of the theory and allows for an unambiguous separation of ultraviolet (UV) and infrared (IR) divergences to arbitrary loop order, making it an alternative to dimensional regularization methods. Nevertheless, compliance between IReg and KLN theorem is not yet proved and a systematic treatment of IR divergences to n-order is yet to be implemented. IReg has been applied to diverse physical computations to two-loop order processes spanning abelian and non-abelian theories with and without supersymmetry. It has been proved to fullfill unitarity, Lorenz invariance and locality. Being a non-dimensional scheme, IReg allows for a systematic treatment of objects that are only well defined in the dimension of the theory such as gamma5 matrices. In this work we will compute a set of processes which will serve as probes for the development of practical computations to deal with UV and IR divergences and test the compliance between IReg and the KLN theorem at NLO and beyond. We intend to consider processes involving scattering and decay of Standard Model particles, both with massive and massless particles in the final state first at NLO. These computations aim not only to shed light on the compliance of IReg to the KLN theorem but also to study the technique in a framework where different scales and physicals thresholds are present. Once the NLO computations are well established, we propose to address the N2LO contribution for the same set of processes described. In accomplishing these tasks, computational routines will be developed, which will help in the dissemination of the IReg method.
Pion- and Kaon-induced Drell-Yan cross section at the AMBER experiment from CERN/SPS
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Catarina Quintans

Co-Supervisor: Pedro Abreu

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The AMBER experiment is a fixed-target experiment at SPS, CERN. It was recently approved, and one of the physics goals is to study the pion- and kaon-induced Drell-Yan process. This process allows privileged access to the pion and kaon structure. At AMBER the valence, sea, and gluon contributions in the pion will be characterised with unprecedented accuracy, using high-intensity pion beams of both charges impinging in different nuclear targets. The simultaneously collected kaon-induced samples will provide input for the until now basically unknown kaon structure. This proposal aims to analyse data from Monte-Carlo simulations and AMBER physics Runs. Machine learning techniques will be tested and/or developed to address different aspects of the analysis, like the dimuon acceptance calculation in N-dimensions space; beam particle identification using Cherenkov counter detectors (CEDARs); and process separation for improvement of the Drell-Yan signal purity. The effectiveness of these methods will be compared to the standard dimuon approaches used so far. The work plan foresees an important CERN on-site presence, since the student will actively participate in the preparation and detector commissioning, and on the data-taking, during the beam tests and physics Runs of AMBER.
Indirect detection of dark matter in the galaxy
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rui Santos

Co-Supervisor: Milada Margarete Mühlleitner

Institution: FCUL (Universidade de Lisboa)

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

The search for Dark Matter (DM) is one of the main goals of present high energy physics and astrophysics experiments. A large number of direct and indirect detection experiments together with searches at the Large Hadron Collider (LHC) have so far provided only bounds on the DM mass and couplings. In recent years the community has invested in building a large number of different experiments to indirectly search for dark matter. These experiments cover an energy range from below the MeV to above the EeV. The searches include neutrino telescopes, searches with X-Rays, Gamma Rays, Micro and Radio Waves and Charged Cosmic Rays. They will therefore provide a comprehensive scan of a very wide range of possible dark matter candidates. In fact, the next decade will be that of indirect searches for DM. The groups at the Centro de Física Teórica e Computacional da Universidade de Lisboa (CFTC-UL) and Karlsruher Institut für Technologie (KIT) have a vast experience in extensions of the Standard Model (SM) where a dark sector is included. The dark sectors have been investigated by the group in direct detection and LHC observables both at tree-level and at next-to-leading order. A number of codes that soon will be available for the community are being built by the group to optimize the searches. The plan of the thesis is to start from simple extensions of the Standard Model (SM) and understand what is the contribution that each experiment can give to probe the dark matter sector of the model. The already available code MadDM will be used as our starting point and new modules will be developed to deal with the experiments that are still not accounted for in the code.
New Physics and Vector Like Fermions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Joaquim Silva-Marcos

Co-Supervisor: Gustavo Castelo Branco

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

The central focus of this thesis proposal will be on the development of models with vector-like fermions (VLFs). The main topics to be covered are the development and use of (new) concrete tools to test physics beyond the SM and explore NP models which are consistent with the Electro Weak Precision Measurements (EWPM) of the current and of future data, coming from LHC or others. While developing these new physics (NP) models we aim to achieve exciting and impactful predictions which may be able to point experimentalists to look for new exotic phenomena. We shall also focus on very sensitive CP violation measuring parameters such as epsilon_K, epsilon'/epsilon or others, which may pose strict restrictions to these models and their content. We will look for alternative forms of generating the mixings and masses of the lighter quarks with the introduction of vector-like quarks (VLQs) and shall look for new possible sources of CP-violation in both the quark and lepton sector with VLFs. The CKM unitarity problem, is also an important problem which we will be addressed in the context of VLQs as well as the NP effects it entails. Currently, one of the main issues at the LHC is the search for new heavy fermions, e.g. quarks with masses beyond the top quark, as is the case of a heavy-top and which occurs naturally in models with VLQs in the up sector, or in the case of the leptons, the search for heavy Majorana neutrinos. We are interested in exploring the regions of parameter space where VLF models are experimental allowed and potentially predict a new mass scale beyond the EW scale. With this in mind, we will be studying predictions for processes, possibly, to be witnessed at the LHC, as e.g. the hypothetical decays of these new heavy fermions. Thus, a strong interaction with experimentalists at LIP/CERN will be required. The student will conduct research at both the Centro de Física Teórica de Partículas (Lisbon) and Instituto de Física Corpuscular (Valencia).
Testing Beyond the Standard Model Theories with extra scalars or vectors
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ivo de Medeiros Varzielas

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

Multi Higgs Doublet Models (MHDM) refer to theories that are an extension of the Standard Model (SM), which predicts the existence of more than one Higgs boson. These models are motivated by various reasons, such as providing candidate dark matter particles and predicting new phenomena that could be observed at high-energy colliders like the Large Hadron Collider (LHC). The Three Higgs Doublet Model (3HDM) is a specific variant of MHDMs which proposes the existence of three Higgs doublets instead of one, as in the SM. The 3HDM can be further divided into different types, depending on the Higgs doublets Yukawa interactions and the symmetry imposed on the scalar potential. Depending on the choice of model parameters, there can be distinct phenomenology, including tree-level flavor-changing neutral currents. We plan to study exact symmetries in the 3HDM and the effects of soft-breaking terms. We will also study new phenomena that could be observed at high-energy colliders like the Large Hadron Collider (LHC), such as additional scalar or pseudoscalar particles, in order to constrain the parameters of the models.
Exploring Quark-Gluon Plasma effects in the forward region
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Liliana Apolinário

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Ultra-High Energy Cosmic Rays interact with the Earth’s atmosphere producing Extensive Air Showers (EAS) at very high energies, which are not accessible at the Large Hadron Collider (LHC). The number of muons at the ground, measured by ground-based experiments like the Pierre Auger Observatory, is a key-observable to infer the mass composition of cosmic rays. However, LHC-tuned hadronic interaction model simulations, like EPOS-LHC, have been consistently predicting a lower muon production than the data obtained from measurements of EAS. This long-lasting problem is known as the Muon Puzzle and it shows itself for center-of-mass energies greater than 8 TeV, which is still within the reach of the LHC. The formation of Quark-Gluon Plasma (QGP) in the first interaction of EAS has been proposed as a possible solution and has led to the development EPOS-QGP, a new purely phenomenological hadronic interaction model that accounts for more visible QGP effects than its predecessor EPOS-LHC. The goal of this research work is to study the possible behavior of QGP in the forward region and in small systems, assessing if it can be formed in EAS and explain the Muon Puzzle, by further studying this new promising model. After determining its key-parameters for QGP formation and assessing their impact on air showers and on macroscopic collision parameters, the model shall be confronted with LHC and Auger data, especially from the p-O and O-O collisions of Run 3 and from the AugerPrime upgrade. Focus will be given to the EAS muon distributions, which have been shown to be sensitive to the different shower energy scales, with the model being tested both at LHC energies and higher, reaching a center-of-mass energy of about 400 TeV. This work will limit the future findings of the next hadronic accelerator, the Future Circular Collider, while it paves the way for the study of hadronic physics in air showers, improving our understanding of the Universe and of the Standard Model.
Light and Ultralight Dark Matter: exploring novel synergies between particle physics, strong gravity and cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Roman Pasechnik

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

This thesis proposes a synergy between the areas of strong gravity, cosmology and particle physics in order to explore the Feebly Interacting Particle (FIP) DM paradigm. Contrary to the typical approach taken by the strong gravity community, this thesis aims the construction of concrete particle physics models where ultralight DM particles can emerge either as pseudo-goldstone bosons or as vector bosons, in such a way that they can reveal themselves in the form of stable halos around compact astrophysical objects. However, such halos are only viable when the Compton wavelength of the field approximately matches the gravitational scale of the compact object. For the known astrophysical objects, such as black holes, whose mass is in the range of 1 and 10 to the 10 solar masses, this means that such bosonic particles must have masses between 10 to the minus 10 and 10 to the minus 20 eV. The presence of an ultralight bosonic sector implies further bosonic particles that are not necessarily ultralight, and perhaps at the reach of the LHC if their mass is larger than 1 GeV. Additionally, unstable topological defects may emerge in a pseudo-Nambu-Goldstone (pNG) DM cosmology, which produce gravitational waves in the final state and can be probed by the current experiments. Furthermore, for models featuring neutrino mass generation mechanisms, a sterile neutrino can also become a fermionic DM candidate with masses in the keV-MeV range. In this thesis, a catalog of models that can consistently predict light and ultralight bosons as well as sterile neutrinos will be constructed. These are extraordinary candidates to offer multi-component DM which will be studied and confronted with data both from the gravitational, collider, and direct detection channels.
5D calorimetry at the HL-LHC: hard real-time embedded architectures for system testing and production
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: André David

Co-Supervisor: Nuno Roma

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CERN Experimental Physics Department

Abstract

The upcoming High-Luminosity phase of the Large Hadron Collider (HL-LHC) requires the replacement of the CMS detector endcap calorimeters with the new High-Granularity Calorimeter (HGCAL). The HGCAL detector will comprise more than 6 million channels to provide precise sensing and measurement of 3D position, timing, and energy of particles produced in the collisions. The HGCAL electronics comprise a large and rather complex processing system, whose capability will have to be scaled by several orders of magnitude to satisfy the demands required by this upgrade and lay out the blueprint for future detectors. In particular, about 100 Field Programmable Gate Arrays (FPGAs) will be used in the off-detector back-end to perform the configuration, timing, control, and monitoring of the on-detector ASIC electronics. While several IP blocks have been developed, they only provide proof-of-concept functionality for the different functions and are just a first step on the way to the full 100-FPGA detector system. Those blocks need to be tested and integrated into increasingly larger systems. A rather demanding challenge that is still to be tackled is the scaling up of these IPs, from their existing (small scale) prototypes. Integrating them in gradually larger and more complex systems as needed to support the construction of the detector until 2028 is not a trivial task, as reliability needs to be ensured at every single step. Under these premises, the proposed PhD workplan focuses on the definition of architectures and attending testing frameworks to support the scalability and the integration of the several (existing and/or to be defined) HGCAL data-processing elements and control systems. The devised (modular) architectures will have to comply with the demanding requisites (in terms of data throughput and interface) that characterize the heterogeneous nature of the HGCAL data processing ecosystem.
Development of a 4D tracking detector for the ATLAS Experiment at CERN
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Antonio Onofre

Co-Supervisor: Stefan Guindon

Institution: Universidade do Minho

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The current thesis aims to contribute to the development of an innovative 4D tracking detector to be installed in the ATLAS experiment at CERN. During the course of the thesis, the student will contribute to tests of the assembly procedure, monitoring, and testing of the cooling performance on a full-scale half-disk detector inside a clean room environment. Moreover, the student will be able to work on Low Gain Avalanche Detector (LGAD) sensor testing and front end ASIC board characterisation, and to participate in test-beam activities at the SPS facility of CERN. This work will involve assisting in the setup, calibration, data-taking and final data-analysis of test-beam activities.
Quantum Simulation of Particle Scattering Processes
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Yasser Omar

Co-Supervisor: Joao Seixas

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Portuguese Quantum Institute

Abstract

Quantum computation (QC) is a new and promising paradigm to accelerate challenging computations, in particular simulations of quantum systems. This ongoing project aims at studying and developing new and more efficient techniques for quantum simulation of scattering processes in the framework of lattice quantum field theory. The topic of the ongoing first year is quantum simulation of scalar field. The scalar field is not only simple enough to isolate the difficulties of quantum simulation, but it is also a first step towards quantum simulation of the Standard Model and in particular of the Higgs sector. The first goal here is to extend known results to simulate scattering of bound states, which is absent in the literature. Then the focus will move to fermionic gauge theories. This will introduce new difficulties. One crucial step for any quantum simulation is finding an efficient way to encode the degrees of freedom (DOF) of a theory into a qubit system. This is particularly challenging for fermionic gauge theories for two main reasons: 1) the tensor-product structure of qubits is not well suited for anti-commutation relations; 2) gauge theories have nonphysical redundancies that have to be eliminated. The second goal of this project is to tackle this problem and to find better ways to encode gauge theories. The full Standard Model in the huge range of energies experimentally accessible today is beyond the capability of any conceivable computational device. Effective field theories (EFT) will play a crucial role in factorizing the full problem into more accessible problems and in separating the energy scales involved in scattering events like at LHC. Part of the work will consist in identifying the effective theories that are at the same time most suited to tackle classically intractable regimes and to reduce the number of redundancies as much as possible. Combining the techniques and results from the first two parts will be the final goal of the project.
Analysis of asymptotically flat and asymptotically de-Sitter spacetimes with conformal methods
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Edgar Gasperin Garcia

Co-Supervisor: Alex Vano-Vinuales

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The asymptotic properties of spacetimes play a central role in many physical aspects of General Relativity (GR), in particular for the concept of gravitational radiation. One of the crucial concepts introduced for the realisation of the latter, was the use of conformal compactifications introduced in General Relativity by R.Penrose to describe in a geometric way the notion of infinity. The formulation that takes Penrose’s idea of conformal compactification --in conjunction with the theory of partial differential equations-- to its ultimate consequences are Conformal Einstein Field (CEFE) equations introduced by H. Friedrich in [1]. These equations have been used for establishing (semi)-global non-linear stability results de-Sitter and Minkowski spacetimes and some partial global non-linear stability results for black hole spacetimes such as Schwarzschild-de Sitter [2]. Although these equations have been available since 1980 the numerical exploration of spacetimes using the CEFEs is still in its infancy compared with other formulations since they have not been systematically exploited as other formulations of GR. One of the alternatives to the CEFEs is the use of hyperboloidal foliations and scri-fixing techniques and more standard formulations of the Einstein Field Equations such as the Generalised Harmonic Gauge (EFE-GHG). These have been exploited for numerical implementations [7] and for mathematical analysis [8]. By construction, hyperboloidal foliations reach the null-infinity but stays away from the region close to spatial infinity. The CEFEs have access to this region via the construction of the so-called cylinder at spatial infinity. These methods, hyperboloidal and conformal, being complementary and grating access to the different regions of spacetimes can be exploited for the analysis of global properties of spacetimes by means of mathematical and numerical methods or a combination of thereof.
High-performance timing detectors for the CMS upgrade at the High-Luminosity LHC and searches for new physics processes
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Michele Gallinaro

Co-Supervisor: Jonathan Hollar

Institution: Universidade de Lisboa

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

After the successful first runs of the LHC where the Higgs boson was discovered, the collider and its experiments are gearing up to produce and collect a ten-fold larger data set which will extend the sensitivity to new physics in direct and indirect searches for processes with low production cross sections and harder signatures. This dataset will considerably improve the precision in the measurement of properties of the Higgs boson, including the possibility to measure its triple self-coupling for the first time. To achieve the high intensity in the second phase of the LHC, the machine is expected to provide unprecedented luminosity of around 5x10^34 cm^{-2} s^{-1} with an average of 140 to 200 collisions occurring each bunch crossing. This poses a challenge to the detectors which will have to cope with a harsh radiation environment and will be subject to a high flux of is also a challenge for the reconstruction of the events to be acquired and used to improve the measurement of the Higgs properties to a percent-level precision and search for new physics processes. A high Precision Proton Spectrometer (PPS) has been taking data as a subsystem of the CMS experiment. It uses a timing detector in order to measure the time of flight (ToF) of the two forward protons produced in the interaction point in the CMS detector. Considering central exclusive production processes (pp->pXp), 10 ps time resolution detector would provide 2.1 mm spatial resolution on the vertex position and improve of a factor of about 25 the background pile up suppression.
Neutrino-plasma interactions: laboratory studies with plasma metamaterials
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Hugo Terças

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Instituto de Plasmas e Fusão Nuclear -IPFN

Abstract

Neutrinos are particles that interact only through the Weak-Interaction. Nowadays, detection techniques are efficient only for high-energetic neutrinos. The single-particle interaction produces Cherenkov radiation, whose properties lead to neutrino characteristics. To probe the ultra-low energetic part of the neutrino spectra, we may exploit a collective-interaction scheme. When a neutrino flux interacts with plasmas, as in supernova events, instability occurs, and plasma oscillations (plasmons) are generated. The detection of such plasmons can be used to infer neutrinos characteristics, like the Cherenkov radiation. Solid-state electron plasmas are easy to control in laboratory experiments. Therefore, we focus on defining a metamaterial with tunable dispersion relation. The objective is to exploit the coupling between a neutrino flux and an electron distribution, the goal is to maximize the energy transfer and, thus the amplitude of the neutrino-generated plasmon. To exploit the innovative neutrino-plasma detection technique, we will rely on Kinetic theory and Quantum plasmadynamics, which will be used to derive the cross-section of the plasmon generation due to the neutrino distributions; numerical simulations will evaluate the specifics and feasibility of metamaterial-based detection.
Challenging Lambda with Euclid and Beyond
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The growing amount of observational evidence for the recent acceleration of the universe unambiguously demonstrates that canonical theories of cosmology and particle physics are incomplete (if not incorrect) and that new physics is out there, waiting to be discovered. The most fundamental task for the next generation of astrophysical facilities is therefore to search for, identify and ultimately characterise this new physics. The acceleration is seemingly due to a dark component whose low-redshift gravitational behaviour is very similar to that of a cosmological constant. However, currently available data provides very little information about the high-redshift behaviour of this dark sector or its interactions with the rest of the degrees of freedom in the model. It is becoming increasingly clear that tackling the dark energy enigma will entail significantly extending the redshift range where its behaviour can be accurately mapped. A new generation of ESA and ESO facilities, such as Euclid, the ELT, and the SKAO have dark energy characterization as a key science driver, and in addition to significantly increasing the range and sensitivity of current observational probes will allow for entirely new tests. The goal of this thesis will be to carry out a systematic exploration of the landscape of physically viable dark energy paradigms and provide optimal discriminating observational tests. The work will initially focus on Euclid (whose launch is fast approaching) and will gradually broaden to explore synergies and probe combination with the SKAO and ANDES. The work will be done in the framework of the Euclid TWG, and the student will be a member of Euclid as well as of the FCT Phi in the Sky grant.
Probing the nature of the neutrino with large scale dark matter detectors
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Alexandre Lindote

Co-Supervisor: Claudio Frederico Pascoal da Silva

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Neutrinoless double-beta decay (0𝜈𝛽𝛽) is one of the most important topics in modern particle physics, offering a unique opportunity to discover physics beyond the Standard Model. In a neutrinoless double-beta decay, a nucleus with mass number A and charge Z undergoes the decay (A, Z) → (A, Z+2) + 2e- but no neutrinos are emitted. This is not allowed in the Standard Model of particle physics as it violates the conservation of the lepton number, hinting that leptons play a part in the observed Universe matter/antimatter asymmetry. It would also probe the Majorana nature of neutrinos, i.e. if neutrinos are their own antiparticles, and would provide information about the neutrino mass hierarchy and effective mass. As such the observation of this process would be a breakthrough in modern physics. Xe-136, which comprises 9% of natural xenon, is one of the few isotopes that are expected to undergo this decay. This makes xenon detectors designed towards the search for dark matter particles extremely competitive in the search for this process, given their large masses and extremely low backgrounds, reaching sensitivities similar to dedicated 0𝜈𝛽𝛽 experiments. LUX-ZEPLIN (LZ), which started operating in late 2021, is one of such detectors. Employing ten tonnes of liquid xenon, it contains a total of 630 kg of Xe-136 in its sensitive region. A preliminary study using simulated data showed that it could reach a half-life sensitivity of 1.06x10^26 years after 1000 days of operation, similar to the current best results. This study used conservative assumptions on the background assessment, energy resolution and background discrimination that can be significantly improved with real data. A next generation (G3) detector is already being planned, with a total mass up to 10x larger, which can lead to a half-life sensitivity 100x higher than LZ, leading to the confirmation (in case of an observation) or exclusion of the inverted hierarchy for the neutrino masses.
Probing ultralight bosons with extreme-mass-ratio-inspirals
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Richard Brito

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

Gravitational-wave (GW) observations have an enormous potential to help solving long-standing problems in fundamental physics. Recently, it has become clear that these observations open new opportunities to help us to characterize and identify dark matter [1]. Many proposals have been put forward about how GWs can gives us information about dark matter and its nature [1]. This project will be devoted to study one of such proposals. The main goal will be to study how the existence of ultralight bosons (particles with masses below the eV scale proposed as dark matter candidates (see e.g. [2]) could affect the GW emission from binary black holes (BHs). These particles are specially interesting in this respect because they can have Compton wavelengths as large as astrophysical BHs, leading to a plethora of interesting effects (see e.g. [2,3]) such as the formation of very long-lived structures, or “boson clouds” around spinning BHs that can be observed through several channels [3], including through GW observations. Recent developments have shown that, if existent, ultralight bosons could significantly modify the dynamics of binary BH systems leaving clear imprints in the GWs emitted the binary (see e.g. [4,5,6]). Within this context, in this project we will consider the so-called extreme-mass-ratio inspirals (EMRIs), binary systems in which a stellar-mass compact object, orbits a supermassive BH with millions of solar masses. These sources are expected to be detected by the future space-based GW detector LISA with extreme precision [7]. Most studies considering EMRIs evolving within boson clouds relied on non-relativistic approximations [4,5,6] and simplistic assumptions about the orbital dynamics, insufficient for an accurate description of these systems. This project will go beyond those simplifications by studying EMRIs evolving within bosons clouds using a fully relativistic setting: a necessary stepping-stone in order to be prepared for the future LISA mission.
Applying Fractional Calculus in Gravitational Collapse
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Paulo Moniz

Co-Supervisor: João Marto

Institution: Universidade da Beira Interior

Host Institution: CMA-UBI – Centro de Matemática e Aplicações

Abstract

The research that will eventually be conducted to write a PhD thesis within this proposal involves using a seldom used mathematical technique in high energy physics, but only because the HEP community has not been aware. Otherwise, it has been employed in many domains of physics: e.g. including fractional calculus in atomic or solid-state physics. The possibilities are pretty interesting as far as gravitational settings are concerned. In this proposal, we will investigate (analytically, whenever possible, and numerically) fractional differential calculus and subsequent equations that generalize well-known ones in gravitational physics. We aim to consider the equations governing gravitational collapse either classically or from a quantum (semi-classically) perspective with several fractional derivatives. This may allow making predictions and contrast them to establish which limits or ranges for the fractional derivatives are permitted, given known gravitational data. Fractional quantum gravity is very much in its infancy, and many cases need to be investigated.
Astrophysical tests of gravitational physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Co-Supervisor: Filipe Mena

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The observational evidence for the acceleration of the universe implies that our canonical models of particle physics and cosmology are incomplete, and new physics remains to be discovered. The search for theoretical extensions of the standard model is driven by observations, which provide strong restrictions. This thesis will draw upon ongoing and forthcoming improvements in the sensitivity of tests of several pillars of LambdaCDM, including traditional datasets but also tests of the Einstein Equivalence Principle (both locally and in astrophysical systems), the distance duality relation and the cosmological principle to quantitatively explore and constrain relevant extensions of the standard model. Our starting point will be cosmological models including torsion, which provide a physically well-motivated and comparatively simple testbed. Subsequently, the same approach can be applied to other paradigms. The goal is to provide a statistically robust testing pipeline for these paradigms, which can be applied to current and next-generation datasets, such as Euclid, which are of strategic interest to Portugal and specifically to the host institution.
Genesis of matter and radiation with primordial black holes
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: João Rosa

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

In this research proposal the candidate will explore the role of primordial black holes in the cosmic history, namely in the generation of matter (baryonic and dark) and radiation, with the goal of explaining the origin of their present abundances. The candidate will explore different scenarios for primordial black hole formation in the early Universe and different types of extensions of the Standard Model of particle physics that include dark matter and inflaton field candidates, as well as the necessary non-dynamical ingredients for baryogenesis. The goal of this research proposal is to investigate whether such primordial black holes can produce different particle species through both rotational superradiance and Hawking emission, performing detailed simulations of the evolution of the black hole properties and the number of particles produced of each species, from formation until the present day. This will involve both analytical and computational methodologies, and take into account the associated particle phenomenology (decays, scattering processes, etc). Different observational signatures of these processes will also be explored, considering electromagnetic and gravitational wave emission by the primordial black holes and the particles produced, potentially also including neutrinos and cosmic rays.
Signatures of ultralight bosons around black-holes: impact of non-gravitational interactions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Richard Brito

Co-Supervisor: Chen Yuan

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The detection of gravitational waves has opened a new era for the study of the Universe, giving us a new tool to probe the nature of compact astrophysical objects and their environments. In the coming decades, a variety of current and future experiments will continue to study gravitational waves, such as LIGO/Virgo, LISA, Einstein Telescope (ET), and others, providing unique opportunities to solve a variety of longstanding problems in astrophysics, cosmology, and particle physics. In particular, the possibility to exploit gravitational wave detectors to study dark matter has recently gained a lot of interest. An interesting source of possible detectable gravitational waves are boson “clouds” that can form around spinning black holes. These clouds are composed of ultralight bosons: particles with masses below the eV scale predicted in a multitude of beyond Standard Model scenarios and whose existence has also been proposed as a possible solution to the dark matter problem. The existence of such condensates could have dramatic impact in dynamics of black holes dynamics and lead to a plethora of signatures, including gravitational wave signatures. This thesis aims at exploring those signals, in particular we will aim at understanding how non-gravitational couplings affect such signatures. Namely, studying the shape of these gravitational wave signals and with the appropriate data analysis techniques, we will explore how current (LIGO/Virgo) and future (LISA/ET) facilities can be then used to obtain information about the nature of the particles that compose the clouds.

PT-CERN Call 2021/2

Results

PT-CERN PhD Grants - Call 2021/2 Final Results for Technologies associated to the Portuguese participation at CERN and their transfer to society

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-041 Nuno dos Santos Fernandes
ID-001 Wallison Luiz Anicézio Campanelli
ID-030 Johan Wulff

Results
PT-CERN PhD Grants - Call 2021/2 Final Results for Particle and Astroparticle Physics and associated scientific domains

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-010    Guilherme Machado Santos Soares
ID-035   Maria Alexandra Lima Fernandes
ID-014    Arianna Foschi
ID-005   Dario Vaccaro
ID-002   Etevaldo dos Santos Costa Filho
ID-008   Tiago Gonçalves

Results

Theses (32 theses registered)

Rare Higgs decays and couplings to quarks
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Sandro Fonseca de Souza

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The very high level of background (light quarks are produced abundantly at the LHC, via QCD) renders the signals of direct Higgs decays to light quarks (H->qq) too tiny to be detectable with current data. But there's a catch (!): the quark-antiquark pairs originating from the Higgs decay may bind together (thus forming a meson state). Experimentally, this gives rise to a striking, clean signature: an energetic photon back-to-back to a dilepton resonance, H->Q+gamma. The thesis project consists in the exploration of such rare Higgs decays. The thesis project involves the following tasks: (i) employ the dataset collected by CMS during LHC Run2, to estimate the sensitivity of a baseline analysis, in the Jpsi plus photon channel, which would probe the couplings to the charm quark; (ii) work on the preparation of real-time selection algorithms (trigger), for gaining sensitivity to novel channels, to be deployed for the upcoming LHC Run3, including the phi+photon channel probing the Higgs couplings to the strange quark; (iii) develop machine learning techniques for optimised selection. These are rare processes in the SM that benefit greatly from the HL-LHC phase, and offer sensitivity to the presence of new physics beyond the SM. The research will be carried in the frame of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”. The thesis project is developed within a close collaboration between LIP/Lisbon and UERJ/Rio groups in CMS.
Lepton Flavor Universality
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Alessio Boletti

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Lepton flavor universality (LFU) is deeply ingrained in the symmetry structure of the standard model (SM). Indeed, the SM gauge group SU(3)xSU(2)xU(1) is one and the same for all three generations of fermions. However, recent data provide strong evidence for departures from the LFU principle. Such departures are reported in b quark decays to charged leptons of different flavors (electron, muon, tau). The definite observation of LFU violation, contrary to the SM, would have far reaching implications. It requires the presence of new particles beyond the SM (BSM), such as new gauge bosons (Z') or leptoquarks (LQ). The thesis project explores LFU observables in the most sensitive b->sll quark transitions using CMS data. The thesis project has the potential to deliver the first observation of New Physics at the LHC.
Modified Gravity in Cosmology and Astroparticle Physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: Pedro Avelino

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

General Relativity (GR) is facing many theoretical and experimental challenges and this might be indicative of a need for new gravitational physics. Renormalization approaches to GR clearly showed that counterterms must be introduced, which alter the theory significantly and transform the general relativistic second order field equations to higher order. This implies that extra degrees of freedom,besides the spin-two massless graviton, need to be introduced. In a more general approach, when one tries to explore gravity from the high-energy regime and obtain low-energy physics, one does not recover GR. Adopting string theory as a full theory of quantum gravity, one gets a low energy limit that does not reproduce GR but instead provides a scalar-tensor theory of gravity. Indeed, dilaton fields and their couplings to the spacetime curvature are unavoidable features of string and scalar-tensor theories. It seems that attempts to fully quantize gravity introduce significant deviations from GR and extra degrees of freedom. In high-energy astroparticle physics, modified gravity could shed light on several outstanding problems, e.g. the nature of dark matter as its production in the early universe may give rise to a relic density of the same order of magnitude of the present dark matter density. Modified gravity theories and GR predict different thermal evolution of the universe. Fundamental issues in modified gravity, and particle physics, relate to the origin of the matter-antimatter asymmetry and Leptogenesis. Other issues to be explored are mixing fields, vacuum fluctuations, neutrino oscillations, WIMPS, gravitational waves and the absolute value of the neutrino mass, which could be important tools to probe modified gravity. The ultimate goal of the proposed research program is to devise viable modified gravity models that pass local tests, explain the dynamics of the Universe and be consistent with constraints from high-energy astroparticle physics.
Enhanced Searches with the Pierre Auger Observatory in the Era of Multi-messenger Astrophysics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Raul Sarmento

Co-Supervisor: Ruben Conceição

Institution: Universidade do Minho

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The discovery of ultra-high energy (UHE) neutral particles, whose production is expected by cosmic-ray interactions at the source environment, would allow the identification of the astrophysical sources of UHE cosmic rays and unveil many of the mysteries surrounding their production and propagation. The Pierre Auger Observatory, the world's largest experiment in the study of the highest-energy astroparticles, is being upgraded with new detector technologies to reduce its current systematic uncertainties and accurately determine the mass composition of UHE cosmic rays. This work proposes to investigate how to use the new tools, focusing on a sub-array of surface detectors upgraded with resistive-plate chambers (MARTA) to enhance the observatory's searches for photons. In particular, it will bring Auger to the study of the mysterious sources of fast radio bursts (FRB), by addressing their connection to the emission of high-energy photons. Targeting the recent low-energy extension of the observatory, air-shower phenomenology studies and dedicated data analyses will be developed to perform the measurement of the shower muonic component and access new information near the shower core. Following an assessment of the impact on the overall event reconstruction and photon-hadron discrimination, the findings will be applied to the development of the first search for photons with energies above 10 PeV in association with FRB.
Unravelling Physical Equations from Cosmological and High-Energy Physics Datasets using Symbolic Machine Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: Universidade de Lisboa

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Cosmology is presently based on the construction of physical theories that are compared against observations to constrain model parameters. Despite the success of the present “Concordance” Cosmological Model, there is growing evidence of parameter tensions between Cosmological Probes, depending on the origin dataset. These tensions can be interpreted as opportunity windows for new physics and particles, however, that does not necessarily imply a deeper understanding at the more fundamental level. Alternatively, tensions can be avoided, by construction, if we allow datasets themselves to reveal their preferred laws, without a priori assumptions. In this PhD project, we propose to extract some of these laws directly from data. We will develop, implement and deploy novel algorithms based on symbolic regression and machine/deep learning innovations emerging in the literature to infer data-driven equations and model-independent information directly from cosmological data. We will then apply these methods together with modern astronomical survey data from ESA Gaia and Euclid to derive the underlying profiles of halos, voids and the Universe’s mean background density. This analysis will enable us to confront theoretical predictions that rely on physical model assumptions, including from Particle Physics, about the nature of Dark Matter, Dark Energy and the Cosmological Principle, with the profiles derived from model-independent data. In contrast with most machine/deep learning techniques broadly adopted today, this PhD project proposal has the potential to have an important impact in our understanding of laws in Astrophysics, Cosmology and other areas of Physics, since symbolic techniques result in more interpretable models than possible before.
Biocosmology: evolving state space and simulating the Adjacent Possible  
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Andrew Liddle

Co-Supervisor: Marina Cortês

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Project supervisors Marina Cortês and Andrew Liddle are founding a new scientific discipline that we call Biocosmology. In an ongoing collaboration with Stuart Kauffman (Seattle) and Lee Smolin (Perimeter Institute, Canada), we are proposing a new way of viewing physical laws, particularly emergent phenomena, that can permit incorporation of biological systems into cosmological models. It is the first bridge connecting cosmology and biology, scientific areas which were previously disconnected though lack of a common mathematical framework and tools. Biocosmology allows us to see life through the lens of black holes, dark energy, and dark matter. It is the first quantification, ever, of the value of our planet before the vastness of the cosmos. We will be submitting three papers to initiate this topic at the start of 2022 [1,2,3]. These papers open numerous avenues for further development, and tie in with renewed interest in emergent phenomena across a range of sciences. This includes challenges to the longstanding reliance on reductionist approaches. One of the main principles in our initial work is to allow for the possible evolution of the physical state space of the Universe, as it and its contained biospheres develop. This PhD project has the goal of investigating the consequences of such evolution both from a mathematical point of view through simulations, and from a physical point of view by connecting to ideas of information and entropy, particularly in connection with cosmic horizons. In parallel the student will develop models of fundamental time irreversibility using Cortês and Smolin’s Energetic Causal Set (ECS) framework [4], to create an emergent space-time model that may connect to and underpin these ideas; this particular collaboration is already underway.
The partonic structure of hadrons
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Gernot Eichmann

Co-Supervisor: Alfred Stadler

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Almost all mass of visible matter rests in atomic nuclei and therefore in nucleons, which are complicated bound states of “partons”, namely quarks and gluons, the fundamental degrees of freedom in QCD. However, the structure of mesons and baryons is much more complicated than the naïve quark model suggests and their internal composition is still largely unknown territory. The distribution of quarks and gluons inside hadrons and nuclei, the decomposition of spin and orbital angular momentum, and the role of gluons in the dynamical generation of a hadron’s mass are all urgent questions that need to be answered. The experimental landscape in the forthcoming decades will be shaped by the COMPASS++/AMBER experiments at CERN and the Electron-Ion-Collider (EIC) at Brookhaven, which aim to map out the partonic structure of mesons, nucleons and nuclei and reveal the origin of the glue that binds their constituents. The central quantities of interest are parton correlation functions such as PDFs (Parton Distribution Functions), GPDs (Generalized Parton Distributions) and TMDs (Transverse Momentum Distributions), which encode the spatial and momentum distributions of partons and their spin and orbital angular momentum correlations inside hadrons. The goal of this project is to compute PDFs, GPDs and TMDs with nonperturbative continuum calculations by employing a new technique that has been recently established. This will deliver new insights on the internal structure of hadrons and provide much needed theory support for upcoming experiments at CERN and other facilities.
Signatures of gravitational waves in non-homogeneous cosmologies
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

So far, gravitational waves have been described in the context of homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker (FLRW) models. A more general class of non-homogeneous Lemaître-Tolman-Bondi (LTB) models may be a more natural and observationally consistent alternative to the present homogeneous and isotropic paradigm. Predictions for gravitational waves from the early universe and from astrophysical sources are still missing for this class of models and are necessary for the preparation of the next ESA flagship missions for cosmology: LISA and Euclid. The main objective of this project is to develop the framework of GW generation in LTB, and build realistic simulations of the GW background based on it, using a combination of numerical and Machine Learning methodologies. The plan is to perform a detailed characterization of the properties of the GW signal that will be detected by future GW experiments for this class of models. We will also propose to explore the complementarity between GW and Electromagnetic (EM) surveys, combining information carriers in a multi-messenger approach, to identify cosmological signatures of LTB non-homogeneity in future datasets such as the forthcoming ESA/Euclid satellite data releases.
Coupled tachyonic dark energy: a test in the Euclid era
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Alberto Rozas-Fernandez

Co-Supervisor: Francesco Pace

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The main goal of ESA's Euclid space mission, to be launched in 2022, is to understand the origin of the observed late-time accelerated expansion of the Universe. One tantalising theoretical possibility is to describe the acceleration and the formation of structure in models in which dark energy interacts directly with dark matter. The goals of the proposed thesis are two-fold. First, study the evolution of cosmological structure in the coupled tachyonic dark energy scenario, forecasting Euclid’s ability in testing this hypothesis. For this purpose, we shall consider conformally coupled, disformally coupled, together with models which simultaneously make use of both couplings. The different models will be tested both at background and linear level against the most recent observational data. Second, study the full non-linear regime, producing the first N-body simulations of the coupled tachyon and making therefore the first detailed study of non-linear structure formation under the coupled tachyon hypothesis.
Atomic inputs for probing the r-process in kilonovae
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Sampaio

Co-Supervisor: Gabriel Martínez Pinedo

Institution: FCUL (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

In this proposal we intend to make a relevant contribution to the questions "Where are the heaviest elements in nature produced? And can we identify an astrophysical signature of their production?". Recent studies of the evolution of light curves of kilonovae, and the observation of a kilonova electromagnetic transient associated with the gravitational wave signal GW170817 point to the production of r-process elements in neutron-star mergers.[1] In order to study such electromagnetic signals it is necessary to combine an accurate description of atomic parameters with sophisticated astrophysical simulations. However, atomic data regarding r-process ions, particularly lanthanide and actinide ions, are scarce. For that reason, in this work level energies, excitation/ionization cross-sections and oscillator strengths between individual levels will be calculated for all neutral and charge state lanthanide and actinide ions relevant in the density and temperature range found in the ejecta expansion in a kilonova. For this FAC and MCDFGME codes will be used, as they represent today the state of the art in atomic structure calculations. The results will serve as input for modeling the luminosity curves of kilonovas beyond the local thermal equilibrium (LTE) approximation. The PhD. research activities will be developed at LIP (Laboratório de Instrumentação e Física Experimental de Partículas), Lisbon, Portugal and at GSI (Helmholtz Centre for Heavy Ion Research), Darmstadt, Germany.
Probing CP couplings in ttX production at the Run3 of the LHC.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio Onofre

Co-Supervisor: Miguel Fiolhais

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

In this PhD thesis proposal, we explore CP discrimination, in the associated production of top-quark pairs with generic scalar/pseudo-scalar and vector/axial-vector boson mediators, at the LHC. In addition to the Higgs boson, which may reveal a non-Standard Model (SM) CP (charge-parity) nature of the couplings to heavy quarks, these searches are also looking for hints of Dark Matter (DM) candidates, in simplified models with spin-0 and spin-1 particles, that act as mediators. Events from the associated production (ttX, X=spin-0, spin-1) of top quarks are searched for in the single lepton and dilepton topologies, in proton-proton collisions at the Run3. Following full kinematic reconstruction, a search for specific angular distributions that are sensitive to the CP nature of the mediator couplings, not only to the magnitude of the mixing angle but also to its sign, is expected to be performed with the aim of discriminating, as well, the dominant backgrounds at the LHC from the signals under study. The mass range covered by the searches, focuses on the very low mass region up to masses O(TeV), using the Standard Model Higgs boson mass case, as a benchmark for the CP observables performance. The use of Machine Learning (ML) algorithms, for event classification, is also expected to be performed since it has shown to be particularly promising in the context of High Energy Physics (HEP). These algorithms will be tested in ttX associated production, with completely new coverage of the CP parameter space. The impact on the signal sensitivity is to be quantified in terms of cross-section measurements or 95\% CL limits (in case no New Physics is discovered), using ATLAS data collected at the Run3. State-of-the-art Monte Carlo simulations like MadGraph5 with specific UFO models will be used. In addition, a global fit using ML algorithms will be performed to constrain the Wilson coefficients within the Standard Model Effective Field Theory (SMEFT).
New Physics and Vector Like Fermions
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Joaquim Silva-Marcos

Co-Supervisor: Francisco Botella

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

The main focus of this thesis proposal will be on the development of models with vector-like fermions (VLFs), but multi-Higgs models shall also be explored. The topics to be covered are, amongst other, the development and use of (new) concrete tools to test physics beyond the SM and explore NP models which are consistent with the Electro Weak Precision Measurements (EWPM) of the current and of future data, coming from LHC or others. While developing these NP models we aim to achieve exciting and impactful predictions which may be able to point experimentalists to look for new exotic phenomena. We shall also focus on very sensitive CP violation measuring parameters such as ε_K, ε’/ε or others, which may pose strict restrictions to these models and their content. Additionally, in our analysis of models, we will use other powerful tools based on weak-basis invariants. We will look for alternative forms of generating the mixings and masses of the lighter quarks with the introduction of vector-like quarks (VLQs) and shall look for new possible sources of CP-violation in both the quark and lepton sector with VLFs. The CKM unitarity problem, is also an important problem which we will be addressed in the context of VLQs as well as the NP effects it entails (e.g. flavour changing neutral currents). Currently, one of the main issues at the LHC is the search for new heavy fermions, e.g. quarks with masses beyond the top quark, as is the case of a heavy-top and which occurs naturally in models with VLQs in the up sector, or in the case of the leptons, the search for heavy Majorana neutrinos. With this in mind, we will be studying predictions for processes, possibly, to be witnessed at the LHC, as e.g. the hypothetical decays of these new heavy fermions. Thus, a strong interaction with experimentalists at LIP/CERN will be required. The student will conduct research at both the Centro de Física Teórica de Partículas (Lisbon) and Instituto de Física Corpuscular (Valencia).
Confinement in the Complex Plane
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Paulo Silva

Co-Supervisor: David Dudal

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

This thesis proposal will allow us to study the properties and the dynamics of compact QED on the lattice, having in mind a sensible contribution to the understanding of other gauge theories, such as QCD. In particular, we will focus on the behaviour of the photon propagator and the corresponding Schwinger and spectral functions in the confined and deconfined phases. In addition, we include dynamical fermions and new algorithms to avoid topological freezing having in mind more realistic simulations.
Impacts of modified gravity in high energy astroparticle physics and cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: João Rosa

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The Standard Model of particle physics and the standard model in cosmology are both in very good agreement with experiments and observations. However, they are in contradiction with each other, or, at the very best, they remain incomplete. To complement the remarkable work that is being done in particle physics to search for physics beyond the standard model, we will be studying different cosmological models and modifications to gravity. In particular, we will be exploring cosmological reconstruction methods, dynamical systems and future singularities. The early universe will be an epoch of particular interest, in which the intersection between particle physics and cosmology is crucial. We will be considering baryogenesis, leptogenesis and relic abundances in modified gravity models.
Arrow of Time: its origin in the Universe.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Marina Cortês

Co-Supervisor: Andrew Liddle

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Time always moves in the same direction, it always increases and never decreases: we always remember the past and never the future. This asymmetry of time is universal, from scales on Earth up to cosmological scales. We receive light that galaxies emitted long ago in the past and never receive light they emitted in the future. This time asymmetry is not reflected in the majority of physics laws which are time symmetric, they work in the same way whether time is increasing or decreasing. In fundamental physics time is symmetric, and we attribute the cosmological arrow of time to very unusual initial conditions in the beginning of the universe. These conditions are so special that their probability is of order 1 in 10^90 or less. Why the universe started in such an unlikely state is a question to which we have no answer in cosmology. In this work we investigate whether the time asymmetry may already be present in the fundamental laws, which would avoid having to attribute it to very special initial conditions at the Big Bang. We construct models that simulate such a time asymmetry, and we will run simulations with these models from both existing and new code. The goal is to infer, from the results of the simulations, what the properties of physics are if it is fundamentally time asymmetric.
Measurement of Collider Neutrinos with the SND@LHC Experiment
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Alberto Blanco castro

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Neutrinos are produced abundantly at colliders, still collider neutrinos have yet to be detected. The LHC will deliver the highest energies yet of man-made neutrinos, and their detection will be a milestone. This will be achieved at the SND@LHC experiment, which is located away from the ATLAS interaction point, near the beam line direction. The experiment is being assembled before the start of Run3, and features technology from LIP in the Muon Detector system. The thesis will involve participation in the commissioning of the Muon Detector system, as well as the optimization of the muon selection algorithms resorting to Machine Learning methods. The experiment will be followed throughout, with participation in data taking and analysis towards the first ever observation of collider muon neutrinos, with energies of over 100 GeV. Additionally, sealed RPCs, a novel technology developed by LIP that is able to surpass the usual need for fresh gas supplies without compromising performance, are strong contenders for upgrades at SND@LHC, as well as for next generation experiments such as SHiP. The SND@LHC experiment will provide a prime testing ground for the sealed RPC technology in regards to muon flux characterization and beam line simulation validations.
Accelerating the ATLAS Trigger system with Graphical Processing Units
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Patricia Conde Muino

Co-Supervisor: Frank Winklmeier

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The LHC is the highest energy particle accelerator ever built. The gigantic ATLAS experiment records proton and ion collisions produced by the LHC to study the most fundamental matter particles and the forces between them. A major upgrade, expected for the years 2025-27, will increase the LHC collision rate up to a factor 7 with respect to the nominal values, to allow acquiring a huge amount of data and pushing the limits of our understanding of Nature. The online event selection system (trigger) is a crucial part of the experiment. It analyses in real time, the 40 MHz event rate, selecting only the potentially interesting collisions for later analysis. After the LHC upgrade, the estimated increase in collision rate, and consequently event size, will lead to much longer event reconstruction times, that are not matched by the slower expected growth in computing power at fixed cost. This implies a change in paradigm, increasing parallelism and/or using hardware accelerators, such as GPUs or FPGAs. The study of hardware accelerators is also interesting for the offline ATLAS reconstruction software, given the availability of High Performance Computers. The LIP Portuguese team was responsible for the calorimeter reconstruction algorithms of the first ATLAS Trigger GPU prototype. The results obtained showed the potential gain but also the limitations of the architecture and implementation done. The objective of this PhD thesis is to contribute to the design, implementation and optimisation of trigger and offline reconstruction algorithms using GPUs as hardware accelerators. In particular, the project focuses on the ATLAS calorimeter clustering algorithm TopoCluster and its GPU counterpart, the Topo-Automaton Clustering.
Perturbations and quasinormal modes of black holes in modified theories of gravity
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Filipe Moura

Co-Supervisor: Jorge Rocha

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

This project is centered around properties of black holes with higher derivative corrections from string theory. We will perform a complete study of linear perturbations of astrophysically relevant black holes in such higher curvature theories of gravity. We will also consider applications to the dual conformal field theories, through the AdS/CFT correspondence. First, we address asymptotically flat spherically symmetric black hole solutions in d dimensions with leading string-theoretical corrections. Here, we compute the different kinds of gravitational perturbations, study their stability and obtain the corresponding spectra of quasinormal modes in different limits. Moreover, we compute the greybody factors of these black holes. Then, we build new analytical rotating black hole solutions with leading string-theoretical higher order corrections in d=5 dimensions. For these solutions in d=4 and 5 we also study their gravitational perturbations, stability and obtain the corresponding spectra of quasinormal modes, greybody factors and shadows. We also perform these perturbative calculations for asymptotically AdS black holes with higher derivatives in d dimensions. In particular, for d=4 Einsteinian cubic gravity we will translate the output of the gravitational perturbation analysis to three dimensional CFTs to which the theory is dual to, through the AdS/CFT correspondence. We then study the phase structure of these CFTs.
Black holes as engines of discovery
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Vitor Cardoso

Co-Supervisor: Paulo Garcia

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The detection of gravitational waves opened a new window onto the universe and became a powerful tool to understand dynamical astrophysical phenomena such as collisions of black holes. Together with observations of the Event Horizon Telescope and astrometric measurements of GRAVITY, gravitational waves have started to turn gravity research into a data-driven field and providing much needed insights about fundamental physics. The goal of this project will be to investigate the phenomenology of gravity theories to probe the spacetime geometry at extreme conditions in the cosmos. This will be done focusing on the impact of tidal fields on the stability and the shape of accretion disks, studying the effects of nontrivial galactic content, such as dark matter, in the motion of stars close to the galactic center and finally testing the black holes nature comparing the relaxation stage of compact geometries not having an horizon with experimental data.
Seeking coupling signatures between dark energy and neutrinos
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nelson Nunes

Co-Supervisor: Tiago Barreiro

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

This project addresses some of the most important questions in cosmology: Is dark energy accelerating the Universe? Does it interact with neutrinos? Do the latter have varying mass? How can future missions help addressing these unknowns? The project subtends three different steps: The first consists in the construction of a general class of scalar field dark energy models coupled to neutrinos. It also includes the study of their phenomenology. The second step investigates the linear and non-linear smaller scales, by using both analytical and numerical techniques. These will be put to test against the most up-to-date observational data available. The third step is dedicated to forecast the capabilities that future large surveys have to distinguish between compelling models beyond LCDM. The focus will be Euclid, LISA and ELT-HIRES missions, in all of which the Instituto de Astrofísica (IA) has a strong involvement.
Testing the Nature of Light and Ultralight FIP Dark Matter with Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Felipe Ferreira de Freitas

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

This thesis proposes a synergy between the areas of strong gravity, cosmology and particle physics in order to explore the FIP (Feebly Interacting Particle) Dark Matter (DM) paradigm. The deep-learning techniques necessary for these studies will be based on evolutionary optimization algorithms and computer vision methods recently developed both in the context of particle and gravitational wave identification. Contrary to the typical approach taken by the strong gravity community, this thesis aims at the construction of concrete particle physics models where ultralight DM particles can emerge either as pseudo-goldstone bosons or as vector bosons such that they can reveal themselves in the form of stable halos around compact astrophysical objects. However, such halos are only viable when the Compton wavelength of the field approximately matches the gravitational scale of the compact object. For the known astrophysical objects, such as black holes, whose mass ranges from 1-10¹⁰ solar masses, this means that such bosonic particles must have masses between 10⁻¹⁰-10⁻²⁰eV. The presence of an ultralight bosonic sector implies further bosonic particles that are not necessarily ultralight, and perhaps at the reach of the LHC if their mass is larger that 1 GeV. Furthermore, for models featuring neutrino mass generation mechanisms, a sterile neutrino can also become fermionic DM candidate with masses in the keV-MeV range. In this thesis, a catalog of models that can consistently predict light and ultralight bosons as well as sterile neutrinos will be constructed. These are extraordinary candidates to offer multi-component DM which will be studied and confronted with data both from the gravitational, collider, and direct detection channels.
Reaching for PeVatrons with the future Southern Wide-field Gamma-ray Observatory
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Mário Pimenta

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

This thesis focuses on measuring PeVatrons with the future Southern Wide-field Gamma-ray Observatory (SWGO), which will have the ability to survey the Galactic centre. The recent observation of Galatic PeVatron events by LHAASO shows that it is possible to detect those events provided that the experiment covers sufficiently large areas (order of 1 km2) and has excellent capabilities of identifying the gamma-induced shower events amongst the hadronic background, which in their case is done by deploying buried muon detectors. To find a cost-effective solution for SWGO that allows reaching for bigger array areas with an excellent gamma/hadron discrimination, the following strategy will be employed: - investigate the shower characteristics of PeV electromagnetic and hadronically induced showers to identify quantities that might be combined to the measurement of the number of muons at the ground. For instance, a promising idea is to look at the azimuthal correlations, whose fluctuations are expected to be larger for showers of hadronic origin. - develop dedicated analyses to estimate the muon content in air showers on an event-by-event basis. For instance, statistically remove the electromagnetic signal footprint to find muon signals. - optimization of the detector unit, making it as simpler/cheaper as possible. For instance, studying the use of only one PMT per station in the outer regions of the array. - optimization of the array layout configuration. Such shall be done recurring to genetic algorithms to probe a larger phase space with a limited number of simulations. All these tasks are intertwined and should be iterated upon each other. Ultimately, the sensitivity of SWGO to PeVatrons and physics reach should be investigated. The study on the shower characteristics will also be used to improve the determination of the cosmic ray mass composition and hadronic interaction properties, which might shed some light on the so-called EAS muon puzzle.
Searching for new particles with astrophysical compact objects
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Herdeiro

Co-Supervisor: Eugen Radu

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

Dark matter remains a central mystery of modern day science. The elusiveness of dark matter candidates in colliders suggests we further search for its true nature where it was first unveiled - in astrophysics via its gravitational effects. In particular, the new golden age in strong gravity - with the gravitational wave era and remarkable new electromagnetic observations of compact objects - is providing intriguing hints on fuzzy dark matter. Such phenomenological studies start from the construction of appropriate compact objects where such fuzzy dark matter plays a key role, both new types of black holes and horizonless compact objects. The goal of this thesis is to go beyond the simplest fuzzy dark matter models, based on Abelian fields. A dark sector, like the visible one, may contain non-Abelian fields. The impact of such fields on the phenomenology of compact objects, connecting it to gravitational wave and electromagnetic observations, is the central goal of this thesis.
Development of high-performance timing detectors for the CMS forward proton spectrometer
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Michele Gallinaro

Co-Supervisor: Joao Varela

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

A high Precision Proton Spectrometer (PPS) has been taking data as a subsystem of the CMS experiment [1]. It uses a timing detector (either diamond or silicon-based) in order to measure the time of flight (ToF) of the two forward protons produced in the interaction point in the CMS detector. One of the major challenges of operating such detectors at the HL-LHC is the "pileup", or additional collisions occurring in the same proton bunch crossing as the collision of interest. By precisely measuring their ToF, forward protons produced in these collisions can be correctly associated to the correct collision vertex, enabling rare photon-photon interactions to be reconstructed at the maximum pileup foreseen for the HL-LHC. In order to fully resolve all collisions, timing precisions of ~20ps or less will be required. In particular it would greatly improve the rejection of backgrounds in searching for high mass resonances, such as a resonant Higgs pair production [2,3,4]. During Run2 of the LHC, fast timing detectors were operated and achievedresolutions of ~100ps with high efficiency. For the HL-LHC, new technologies will be required to cope with the pileup, radiation, and event rates, both in terms of sensors and readout electronics [5]. The subject of this thesis focuses on the preparation of the detector technology to address the challenges at the HL-LHC by exploring the latest developments in timing detectors and electronics, under extreme radiation. Physics studies aimed at determining the sensitivity to New Physics processes will also be pursued. The research will be carried out in the context of the Portuguese participation in the CMS experiment at the LHC, in the framework of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”.
Big Data Processing and Machine Learning for CLOUD/PS215 at CERN
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Antonio Amorim

Co-Supervisor: Jonathan Duplissy

Institution: FCUL (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The main objectives of this proposal involve the application of AI/Machine learning methods to reprocess large amounts of existing and future CLOUD data to train three different AI systems to: • Replace the non-linear “control system” that presently is carried out by user informed trial and adjustment by a trained automatic AI agent. We propose evaluating, training, and deploying the deep neural networks to act as a CLOUD non-linear “control system”. • Create a tool for automatic identification of new particle formation events (NPF). We propose looking at “banana plots” where the aerosol concentrations for different diameters are plotted over time, applying Region-based Convolution Neural Network methods for image recognition, and identifying and possibly classifying the obtained nucleation events. • Train a deep neural network from the observed evolution of aerosol distribution data to provide the growth rates in several conditions. To apply this model to reference data and estimate its performance.
Testing the WIMP paradigm to the limit
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rui Santos

Co-Supervisor: Milada Margarete Mühlleitner

Institution: FCUL (Universidade de Lisboa)

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

The search for Dark Matter (DM) is one of the main goals of present high energy physics and astrophysics experiments. Many direct and indirect detection experiments together with searches at the Large Hadron Collider (LHC) have so far provided only bounds on the DM mass and couplings. DM candidates, which may be bosons or fermions, arise in many extensions of the Standard Model (SM) in a wide mass range. In recent years there has a been a shift from the so-called Weakly Interacting Massive Particle (WIMP) paradigm to the very low mass region of axions and other very light particles. However, many of the present and future planned experiments for direct and indirect searches, such as e.g., the XENONnT [1], DARWIN [2] and SWGO [3] experiments, together with the high luminosity stage of the LHC and future colliders, will still be focused on the WIMP mass region. Furthermore, many of the simplest models one can build still allow for a WIMP candidate. Hence, even if no DM signal was found yet, we should certainly not rush into declaring the death of the WIMP with still so much to explore. The objective of this work is to test the WIMP paradigm to the limit - will future experiments finally gives us a WIMP, or will we have to find a new paradigm? Higher order corrections can change the limits obtained from the experiments for DM masses and couplings within each model. In some cases, higher order corrections have a dramatic effect on the interpretation of the results. More importantly, it is possible that corrections to similar processes can have a much higher impact in say indirect detection than in direct detection. Therefore, only corrections to all processes involving DM in the three probing modes: direct, indirect and collider, can give us a clear idea of their importance. We expect to give a significant contribution towards answering if we are definitely entering a very light/heavy era for DM or if the WIMP is just in a moribund condition until we finally detect it.
Mapping the Dark Side with Euclid and beyond
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The observational evidence for the acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete. New physics is waiting to be discovered, and forthcoming astrophysical facilities must identify it. The source of acceleration has a low-redshift behaviour akin to a cosmological constant, but current data provides limited information on its high-redshift behaviour and possible interactions. Tackling the dark energy enigma requires extending the redshift range where its behaviour can be mapped. New facilities, such as Euclid, the ELT, and the SKA will enable this, increasing the range and sensitivity of current probes and allowing entirely new tests. This thesis will provide a state-of-the-art exploration of the landscape of physically realistic (as well as observationally viable) dark energy paradigms, with the aim of obtaining optimal discriminating observational tests, in particular between the baseline cosmological constant scenario and dynamical dark energy models. Our ultimate goal is to distinguish between theoretical paradigms, using optimized observational strategies for key medium-term observational facilities in whose preparation, performance optimization and, ultimately, exploitation we will be actively involved. The thesis will focus on Euclid (which the student will join) and broaden to explore synergies and probe combinations with the SKAO and ELT-HIRES.
Free hyperboloidal evolution in axisymmetry
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Alex Vano-Vinuales

Co-Supervisor: Edgar Gasperin Garcia

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

Intimately related to other areas of astrophysics and cosmology is the recently born field of gravitational wave (GW) astronomy. Crucial in the analysis of GW data is the input from numerical simulations in the form of waveform templates, which in turn carry the information from the physics in the strong-field regime described by General Relativity (GR) via numerical simulations, from which the wave signals are extracted. As detector sensitivity increases, it needs to be matched by an improvement in the accuracy of the templates. One very promising and elegant way to get rid of finite-radius-extraction error is to numerically evolve the physical system of interest (e.g. a black hole binary) on hyperboloidal slices: spacelike slices that reach future null infinity, which corresponds to the endpoints of future-directed null geodesics and where global quantities of spacetimes such as energy or radiation are unambiguously defined. Conformal compactification, based on an idea by Nobel-laureate Penrose [3], is a suitable approach to the hyperboloidal initial value problem, further developed by Friedrich [4]. Formal divergences in the equations make numerical implementations of this problem challenging, but previous successful implementations encourage us to follow this promising path. The aim of this project is to generalise the existing free-evolution hyperboloidal spherically symmetric code [24] to axisymmetry, and so i) get closer to a full 3D hyperboloidal infrastructure to simulate binary coalescences and extract GW signals, and ii) couple the axisymmetric Einstein equations to physical content, such as scalar fields, the Maxwell equations and the Yang-Mills fields, to study their phenomenology in a scenario more general than spherical symmetry, and among them consider specially the candidates to fundamental fields. Additionally, the code can also be adapted to describe an Anti-deSitter (AdS) spacetime, and used to study collapse in axisymmetry.
Characterization of liquid argon detectors for next generation neutrino physics
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: José Maneira

Co-Supervisor: Fernando Barao

Institution: Universidade de Lisboa

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The question of how neutrinos may be related to the origin of the matter-antimatter asymmetry in the Universe is one of the fundamental goals of Particle Physics today, and the central motivation to accurately measure long-baseline neutrino oscillations with the next generation of experiments. The technology of liquid argon time projection chambers (LAr TPCs) allows for massive detectors with excellent tracking and calorimetry -- all crucial capabilities to meet the requirements of the next generation of experiments. In this technique, particles ionize the argon, creating free electrons that drift in an intense electric field and are collected in wire anodes planes, with the measured time providing the drift length. A full characterization of the electric field uniformity and the charge attenuation along the drift are essential to guarantee a precise 3D reconstruction of the neutrino interaction and its energy. This requires calibration systems and methods capable of measuring parameters describing those effects with enough granularity in time and space. This project will be based on the development of calibration and characterization techniques of LAr TPCs with cosmic ray muons, intense UV laser beams, and possibly a dedicated radiation source. It will be focused on the DUNE experiment and the second run of its prototype at CERN, ProtoDUNE, that will be installed and start to take data in 2022. The commissioning, operation, and data analysis of ProtoDUNE-II and its new calibration systems, in order to validate the designs, methods, and expected precision, will be the central part of this work plan. Since this validation is a pre-requisite for the future scope of the calibration systems in the DUNE far detectors, it will directly influence the future DUNE calibration and performance. The candidate will integrate the CERN Neutrino Platform team and will play an active role in the ProtoDUNE2 installation.
Big Data Processing and Machine Learning for CLOUD/PS215 at CERN
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Antonio Amorim

Co-Supervisor: Jonathan Duplissy

Institution: FCUL (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

Following a very recent line of research for atmospheric observations, we propose to apply and improve machine learning methods to three different problems in the context of the CLOUD experiment: • The control of the camera driving mechanisms for achieving definite conditions like humidity, ozone creation, etc. To reach a given camera state, a non-linear combination of factors must act along extended periods. The work will replace the non-linear “control system” of CLOUD that presently is carried out by user informed trial and adjustment by a trained automatic AI agent. • Automatic identification of new particle formation events (NPF). The non-linear characteristics of the phenomena in the chamber lead to nucleation events that are only detected by humans looking at “banana plots” where the aerosol concentrations for different diameters are plotted over time. We propose looking at these particular plots as images and applying the Region-based Convolution Neural Network method for image recognition to identify and classify these nucleation events. • A significant quantitative way to express the evolution of the aerosol distribution is the aerosol growth rates. These rates are hard to compute from raw instrument data and must be stripped from many factors like wall effects. We propose to train a deep neural network from the observed evolution of aerosol distribution data to provide the growth rates in several conditions.
Formal and phenomenological studies in the high energy limit of QCD
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Grigorios Chachamis

Co-Supervisor: José Guilherme Milhano

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The subject of this thesis is the theoretical and phenomenological study of the high energy limit of Quantum Chromodynamics (QCD). The understanding of this particular limit, also called Regge limit, in which the colliding energy is much larger than any other hard scale in the process, is one of the most challenging questions in QCD affecting both phenomenology and our formal understanding of QCD as a quantum field theory. The structure of high energy QCD has new effective degrees of freedom, namely, reggeized quarks and gluons (reggeons), which can form bound states, among which the best known are the Pomeron (two reggeons) and the Odderon (three reggeons). The reggeons in the bound states interact with each other via the exchange of gluons. The actual dynamics of these complex interactions is governed by evolution equations which in the case of the Pomeron predict fast increasing cross sections as the energy rises violating unitarity. The best candidate to restore unitarity is parton saturation, where it is assumed that the low-x character of the wave function for an ultrarelativistic hadron or nucleus is governed by an intrinsic hard scale, the saturation scale Qs. Below Qs, the wave functions of the gluons present in the interaction start to overlap which in turn means that gluons begin to recombine leading to a taming of the rise of the cross section. The goals of this research proposal are to study high energy QCD evolution for N-reggeons (N<=4) both with and without saturation, to develop stochastic solutions in momentum space that will be implemented in Monte Carlo codes and to produce theoretical predictions for cross sections which will be contrasted against predictions from multi-purpose Monte Carlos and experimental data. The project will be carried out at LIP within the LIP Phenomenology Group which has members with excellent research record and key contributions to the field of high energy QCD.
Collapse or collide: improved analysis of black hole formation mechanisms
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Rocha

Co-Supervisor: David Hilditch

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

For several decades black holes have played a central role in theoretical physics, and the last few years revealed they are more than constructs of human imagination: we can actually observe them. In the context of general relativity, we have a very good understanding of how black holes are formed under gravitational collapse. Furthermore, there is a clear picture about how black holes can result from high energy collisions. However, this knowledge is based on the assumption that gravity is described exactly by general relativity, even at scales where we would naturally expect quantum gravity to take over. In addition, so far all (semi-)analytic studies of black hole formation processes are unrealistic in the sense that they adopt, at best, perfect fluids to describe the matter involved. This project proposes to take studies of gravitational collapse and shock wave collisions to the next level. On the one hand, relativistic elastic bodies will be considered in gravitational collapse and the impact of the matter’s elasticity in critical collapse and high energy collisions will be assessed. On the other hand, we will also study the effect of higher curvature corrections to general relativity on critical collapse. Such modifications to gravity are expected to leave imprints on critical collapse, since this subject deals with the formation of black holes at arbitrarily small scales. Gravitational collapse in the near critical regime is particularly relevant to understand the distribution of primordial black holes and to investigate the production of very massive hypothetical particles as products of Hawking radiation. Thus, while the research program is tailored to improve our present knowledge concerning black hole formation, it has also important implications for beyond-standard model physics and cosmology.

PT-CERN Call 2021/1

Results

PT-CERN PhD Grants - Call 2021/1 Final Results for Technologies associated to the Portuguese participation at CERN and their transfer to society

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-013 Beatriz Catarina Pinheiro Pereira
ID-008 Nuno Espanha Torrado da Silva
ID-034 Chiara Badiali

Results
PT-CERN PhD Grants - Call 2021/1 Final Results for Particle and Astroparticle Physics and associated scientific domains

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:

ID-017 Borja Serrano Gonçalves
ID-005 João Miguel Martins da Silva
ID-032 Rafael Boto
ID-019 Edoardo Giangrandi
ID-040 João Pedro de Arruda Gonçalves
ID-007 Luis Raúl Torres Rojas

Results

Theses (35 theses registered)

Development of High-Precision Timing Detector for the CMS experiment at HL-LHC
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Joao Varela

Co-Supervisor: Michele Gallinaro

Institution: Universidade de Lisboa

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The HL-LHC requires challenging new particle detectors in order for the experiment to handle the huge protons collision rate. An average of two hundred proton-proton collisions will occur at each bunch crossing, creating an enormous background to rare events in particular those where Higgs bosons are produced. In order to cope with this challenge, the precise measurement of the production time of the charged particles is required. The timing information provides a powerful discrimination of background. The current CMS detectors can achieve a time resolution of the order of 500-1000 picosecond, which is insufficient to maintain the sensitivity to rare physics processes in the HL-LHC era. A strong R&D program towards precise timing of charged particles is now underway aiming at a time resolution of the order of 30-50 picosecond, representing a huge improvement relative to the state-of-the-art. This work focuses on the development of a new Timing Detector based on LYSO scintillating crystals, silicon photomultipliers (SiPM) and dedicated ASIC microelectronics developed in Portugal. The technologies used are at the forefront of R&D in particle physics detectors. It is expected that the developed technologies would be transferred to commercial applications like Light Detection And Range (LiDAR) and Time-of-Flight Positron Emission Tomography. The program of work will integrate a broad range of topics in detector physics and technology, including evaluation of detector prototypes with particle beams at CERN, as well as simulation studies of the impact of the Timing Detector in the CMS physics program.
Rare Higgs decays and couplings to quarks
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Sandro Fonseca de Souza

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

After the discovery of Higgs boson at LHC in 2012 the main focus of the scientists is to probe the decays of this special particle to various other Standard Model particles. The Higgs Mechanism predicts the role of this scalar boson in generating mass of the fundamental particles. Therefore how Higgs boson interacts or couples to other particles is an extremely important question to understand the origin and existence of our universe. Higgs coupling to gauge bosons was discovered at LHC. In 2018 CMS and ATLAS detectors discovered Higgs couplings to heavy fermions such as top and bottom quarks. The recent studies using the data set from CMS detector shows the evidence of muonic decay of Higgs boson. Hence the next step is to probe Higgs decay to second generation quarks using the data from CMS during LHC Run 3. It is very difficult to obtain the traces of this rare decay. Therefore to carry out the investigation of Higgs coupling to light quarks, we can use Higgs decay to a quarkonium state and a photon. The analysis of this decay channel will help to identify the nature of Higgs coupling to other SM particles. Therefore we will be able to probe the properties of Higgs boson. This study will help to decide whether this particle belongs to the Standard Model or first particle beyond the Standard Model.
Rare Higgs decays and couplings to quarks
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Sandro Fonseca de Souza

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Since the discovery of the Higgs boson at the LHC in 2012, by the CMS and ATLAS experiments, the focus has been placed in measuring its properties. In particular, on the determination of how it couples to the other standard model (SM) particles. In 2018, both CMS and ATLAS have detected the couplings of the Higgs to the heaviest quarks: the top (ttH) and the bottom (H->bb). Evidence for the muonic decay was also reported in 2020 by CMS. The next big, and natural, step in this endeavour is to access the H couplings to the lighter quarks. The thesis project consists in the search for Higgs boson decays to a quarkonium state and a photon, using the large dataset collected by CMS at the LHC. The motivation for the study is to experimentally constrain the Higgs-quark couplings, and help decide whether our new boson is indeed the particle at the core of the SM, or detect evidence for contributions of New Physics beyond the SM via the Higgs sector.
What are the signatures of gravitational waves in non-homogeneous cosmologies?
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

So far, gravitational waves have been described in the context of homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker (FLRW) models. A more general class of non-homogeneous Lemaître-Tolman-Bondi (LTB) models may be a more natural and an observationally consistent alternative to the present homogeneous and isotropic paradigm. Predictions for gravitational waves from the early universe and from astrophysical sources are still missing for this class of models and are necessary for the preparation of the next ESA flagship missions for cosmology: LISA and Euclid. The main objective of this project is to develop the framework of GW generation in LTB, and build realistic simulations of the GW background based on it, using a combination of numerical and Machine Learning methodologies. The plan is to perform a detailed characterization of the properties of the GW signal that will be detected by future GW experiments for this class of models. We will also propose to explore the complementarity between GW and Electromagnetic (EM) surveys, combining several wavelengths in a multi-messenger approach, to identify cosmological signatures of LTB non-homogeneity in future datasets such as the forthcoming ESA/Euclid satellite data releases.
Exploring the electroweak vacuum with di-Higgs production at the LHC ATLAS experiment
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ricardo Gonçalo

Co-Supervisor: Konstantinos Nikolopoulos

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Since its discovery, the Higgs boson became a prime tool to search for physics beyond the Standard Model (SM). At the current level of precision, the Higgs boson is compatible with SM expectations. A number of open questions indicate the existence of new physics that could be unveiled as we explore the LHC data. A wealth of experimental results from the ATLAS and CMS experiments, probe the region around the minimum of the Higgs potential, or vacuum. But the shape of this potential is not constrained experimentally. This shape is intimately connected to the breaking of the electroweak gauge symmetry, which resulted in the fundamental forces we experience today. To experimentally constrain this shape we must measure the Higgs boson self-coupling, which is accessible at the LHC through the simultaneous production of two Higgs bosons. This is an extremely rare process that has not yet been observed, and has an expected production rate approximately 1000 times smaller than that for the production of a single Higgs boson. Possible production modes for Higgs boson pairs, HH, at the LHC are gluon-gluon fusion (ggF), vector boson fusion (VBF) and associated production with vector bosons or top quarks.Modifications of the EWSB potential are predicted by several beyond the SM (BSM) theories. Some BSM anomalies on the Higgs boson couplings and interactions could enhance the production rate of Higgs boson pairs by more than one order of magnitude. In some cases, the Higgs boson pair production could be observed even with the current LHC luminosity. In this project, I expect to contribute to enhancing our current knowledge in this important area, which will become one of the most important measurements of LHC experiments. The main goal is to search for the production of Higgs boson pairs, focusing on the VBF production channel. The search will utilize data from Run 3 of the LHC and is expected to result in an important publication of the ATLAS collaboration.
Unravelling Physical Equations from Cosmological Datasets using Symbolic Machine Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: Alberto Krone-Martins

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Cosmology is presently based on the construction of physical theories that are compared against observations to constrain model parameters. Despite the success of the present “Concordance” Cosmological Model, there is growing evidence of parameter tensions between Cosmological Probes, depending on the origin dataset. These tensions can be interpreted as opportunity windows for new physics, however, that does not necessarily imply a deeper understanding at the more fundamental level. Alternatively, tensions can be avoided, by construction, if we allow datasets themselves to reveal their preferred laws, without a priori assumptions. In this PhD project, we propose to extract some of these laws directly from data. We will develop, implement and deploy novel algorithms based on symbolic regression and machine/deep learning innovations emerging in the literature to infer data-driven equations and model-independent information directly from cosmological data. We will then apply these methods together with modern astronomical survey data from ESA Gaia and Euclid to derive the underlying profiles of halos, voids and the Universe’s mean background density. This analysis will enable us to confront theoretical predictions that rely on physical model assumptions, including from Particle Physics, about the nature of Dark Matter, Dark Energy and the Cosmological Principle, with the profiles derived from model-independent data. In contrast with most machine/deep learning techniques broadly adopted today, this PhD project proposal has the potential to have an important impact in our understanding of laws in Astrophysics, Cosmology and other areas of Physics, since symbolic techniques result in more interpretable models than possible before.
Radiation Damage of Optical Components in Scintillator Detectors: from ATLAS/LHC Tile Calorimeter to Future Experiments
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Rute Pedro

Co-Supervisor: Patricia Conde Muino

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The ATLAS Tile Calorimeter (TileCal) is an essential instrument to measure jets, hadrons and the missing energy, participating in the trigger and electron/photon identification. The organic scintillators and wavelength-shifting fibres of the detector are known to degrade with LHC operation, which will be extended by the High-Luminosity LHC (HL-LHC) phase. The objective of the thesis is to study the radiation damage of these optical components, extrapolating their degradation to the HL-LHC. Additionally, the TileCal performance history with dose exposure is a useful and timely input to the design of future collider experiments. Another objective is to explore how the detector design parameters, eg. scintillator/fibre sizes, correlate with the light yield degradation using Machine Learning. The thesis also comprises the optical characterisation of scintillator samples based new organic materials within the scope of an R&D project on scintillators for future detectors.
Measurement of Collider Neutrinos with the SND@LHC Experiment
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Nuno Leonardo

Co-Supervisor: Alberto Blanco castro

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Neutrinos are produced abundantly at colliders, still collider neutrinos have yet to be detected. The LHC will deliver the highest energies yet of man-made neutrinos, and their detection will be a milestone. This will be achieved at the SND@LHC experiment, which is located away from the ATLAS interaction point, near the beam line direction. The experiment will be assembled before the start of Run3, and features technology from the LIP campus in the Muon Detector system. The thesis will involve participation in the installation and commissioning of the Muon Detector system, as well as the optimization of the muon selection algorithms resorting to Machine Learning methods. The experiment will be followed closely throughout, with participation in data taking and the first ever observation of collider muon neutrinos, with energies of over 100 GeV. Additionally, sealed RPCs, a novel technology developed by LIP that is able to surpass the usual need for fresh gas supplies without compromising performance, are strong contenders for upgrades at SND@LHC, as well as for next generation experiments such as SHiP. The SND@LHC experiment will provide a prime testing ground for the sealed RPC technology in regards to muon flux characterization and beam line simulation validations.
Rare Higgs decays and couplings to quarks
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Eliza Melo da Costa

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Since the discovery of the Higgs boson at the LHC in 2012, by the CMS and ATLAS experiments, the focus has been placed on measuring its properties. In particular, on the determination of how it couples to the other standard model (SM) particles. In 2018, both CMS and ATLAS have detected the couplings of the Higgs to the heaviest quarks: the top (ttH) and the bottom (H->bb). Evidence for the muonic decay was also reported in 2020 by CMS. The next big, and natural, step in this endeavour is to access the H couplings to the lighter quarks. The thesis project consists of the search for Higgs boson decays to a quarkonium state and a photon, using the large dataset collected by CMS at the LHC. The motivation for the study is to experimentally constrain the Higgs-quark couplings, and help decide whether our new boson is indeed the particle at the core of the SM, or (even more excitingly) the first particle beyond the SM.
Searching for new physics in the era of Deep Learning and Quantum Supremacy
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Felipe Ferreira de Freitas

Co-Supervisor: António Morais

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

Quantum Computing (QC) leverages the quantum properties of subatomic matter to enable algorithms faster than those possible on a regular computer. Quantum Computers have become increasingly practical in recent years, with some small-scale machines becoming available for public use. This dissertation proposal outlines the challenge of designing quantum algorithms for machine learning and optimization applied to High Energy Physics (HEP) event classification. Machine learning has been used in high energy physics for a long time, primarily at the analysis level with supervised classiﬁcation. The main goal of this thesis proposal is to develop Quantum Machine Learning (QML) approaches, focusing on Variational Quantum Circuits (VQC) to find patterns on the data collected by particle collision events and evaluate the performance of the event classification using both simulators and quantum computing devices. We are particularly interested in distinguishing New Physics (NP) signatures that would point us towards a viable Beyond the Standard Model (BSM) scenario. For this, we intend to utilize QML in combination with self-thought learning (SSL) techniques to quickly achieve a neural network capable of classifying background vs BSM events for different scenarios, namely Leptoquark interactions, a multi-Higgs doublet model with exotic decays and a model with a exotic graviton. In these BSM scenarios there would be lepton-quark currents, two lepton decays from the same scalar vertex with the same charge value, and highly energetic photons from jets emanating from a Kaluza-Klein resonance. We expect the ML apparatus to be able to identify all of these scenarios.
Probing the primordial quark gluon plasma with heavy flavour
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Yen-Jie Lee

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At the LHC we recreate droplets of the primordial medium that permeated the universe in its first microseconds. This hot, dense, coloured medium, the quark-gluon plasma (QGP), is produced in ultra-relativistic heavy-ion collisions. The highest energies attained at the LHC and its state-of-the-art detectors are facilitating tremendous advancements in our understanding of the strong interaction, and of QCD matter at extreme conditions. Such data-driven advances also highlight unexpected behaviour, and the study of the QGP medium is fostered by novel probes facilitated by the large datasets being collected. One such probe is provided by heavy quarks. The bottom quarks are particularly interesting probes, as they are produced early in the collision and thus experience the full evolution of the hot medium. The aim of the Thesis project is the detection and study of b-quark hadrons in heavy-ion collisions (with particular the focus on the still-to-be-detected B0 meson, the rarer Bc meson, and possible exotic hadrons). These novel probes facilitate unique information on the flavour and mass dependence of energy loss mechanisms, as particles traverse the medium, and on underlying quark-recombination mechanisms yet to be observed at these scales. The Thesis project aims at making unique contributions to further our understanding of the primordial medium, by exploring novel probes and unprecedented energies at the LHC
Unification of families and forces meets the Standard Model
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Roman Pasechnik

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

The tremendous phenomenological success of the Standard Model (SM) suggests that its flavour structure and gauge interactions may not be arbitrary but should have a fundamental first-principles explanation. In this thesis, the goal is to explore how the basic distinctive properties of the SM dynamically emerge from a recently proposed unified New Physics (NP) framework [1,2,3] tying together both flavour physics and Grand Unified Theory (GUT) concepts. This framework is suggested by the gauge Left-Right-Color-Family Grand Unification under the exceptional E8 symmetry, the unifying force. Among the most appealing emergent properties of this theory is the Higgs-matter unification with a highly-constrained massless chiral sector featuring a single universal gauge and Yukawa coupling at the GUT scale. Furthermore, as a result of the family symmetry, the proton lifetime can be large enough to allow for low-scale Grand Unification such that, if confirmed in this thesis, can potentially become a paradigm shifting opportunity. At the electroweak scale, the minimal SM-like effective field theory limit of this GUT is consistent with the observed large hierarchies in the quark mass spectra and mixing already at tree level. However, a complete calculation of the SM particle spectra and mixing is necessary to conclusively validate the model. On the NP side, the model can offer three generations of SU(2) doublet vector-like leptons and up to two singlet leptoquarks. With a rather limited freedom but, potentially, a remarkable predictive power, the goal of this thesis is to complete the connection between the GUT theory and its low-scale realization via a full renormalization procedure.
Birds of a feather: seeking the earliest high-energy events in the Universe at the high- and low-energy ends of the spectrum
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Afonso

Institution: Universidade de Lisboa

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The existence of powerful Active Galactic Nuclei (AGN) has now been established well within the first Gyr of the Universe, through observations of optically selected Quasi Stellar Objects (QSOs) up to the currently highest redshift of z ∼ 8. To understand the origins of the supermassive black holes (SMBH) that power QSOs, and how relevant they are to early galaxy and structure formation, it is fundamental to detect AGN activity well within the Epoch of Reionisation. Surprisingly, the sensitivity already exists to find such sources at both extremes of the electromagnetic spectrum, X-rays and radio wavelengths, but all efforts to detect them have so far been unsuccessful. This is presumably due to their expected rareness, but also due to the lack of understanding of the high-energy physical processes present in these youngest extreme sources in the Universe. While surveys to be performed with future telescopes such as Athena (x-rays) and SKA (radio) will overcome the former limitation, the latter suggests correct identification of such ”rosetta stone” sources will remain challenging, as we are still unable to optimise our observations and detection strategies to these sources. Taking advantage of the strong Portuguese participation in these two observatories, this PhD project will explore the synergies allowed by the combination of the unique capabilities of Athena and SKA for the exploitation of the earliest AGN activity. Following-up on our recent work, the student will explore state-of-the-art galaxy and SMBH formation and evolution models, analyse the assumed physical processes and implement new recipes for X-ray and radio emission - taking into account the most recent advances in our understanding of black hole accretion physics. This will improve methodologies for the selection of very high redshift AGN, to be tested in current surveys and used to optimise Athena and SKA observing strategies for the detection of the earliest examples of AGN activity.
Testing string theories through black hole physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Rocha

Co-Supervisor: Filipe Moura

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

This project is centered around properties of black holes with higher derivative corrections from string theory. We will perform a complete study of linear perturbations of astrophysically relevant black holes in such higher curvature theories of gravity. We will also consider applications to the dual conformal field theories, through the AdS/CFT correspondence. First, we address asymptotically flat spherically symmetric black hole solutions in d dimensions with leading string-theoretical corrections. Here, we compute the different kinds of gravitational perturbations, study their stability and obtain the corresponding spectra of quasinormal modes in different limits. Moreover, we compute the greybody factors of these black holes. Then, we build new analytical rotating black hole solutions with leading string-theoretical higher order corrections in d=5 dimensions. For these solutions in d=4 and 5 we also study their gravitational perturbations, stability and obtain the corresponding spectra of quasinormal modes, greybody factors and shadows. We also perform these perturbative calculations for asymptotically AdS black holes with higher derivatives in d dimensions. In particular, for d=4 Einsteinian cubic gravity we will translate the output of the gravitational perturbation analysis to three dimensional CFTs to which the theory is dual to, through the AdS/CFT correspondence. We then study the phase structure of these CFTs.
Cosmological and Astrophysical applications of modified theories of gravity
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: Pedro Avelino

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The late-time cosmic accelerated expansion is a crucial and challenging problem in cosmology. Although the current paradigm has favored dark energy models as fundamental candidates, another possibility arises: modifications to General Relativity, introducing new degrees of freedom to the gravitational sector. We propose exploring the viability of a plethora of such models (consistently analyzing the reproduction of all the cosmological epochs) by considering generalizations of the Einstein-Hilbert action, including "quadratic Lagrangians", involving second order curvature invariants; Lagrangians which, in addition, also include couplings to the matter sector and also generalized scalar(vector)-tensor gravity theories, where scalar(vector) fields play gravitational roles that can be perceived, in an appropriate frame, as couplings to matter. The fundamental goals are to study the theoretical issues of the extra degrees of freedom and, finally, the astrophysical applications of all these classes of models, including (but not limited to) black hole solutions.
Disentangling and Quantifying Jet-Quenching With Generative Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At very high energies or densities, quarks and gluons can produce a new state of matter known as Quark-Gluon Plasma (QGP), which is observed in heavy-ion collisions at modern colliders. Due to the non-perturbative nature of Quantum Chromodynamics (QCD), which is responsible for the interactions and dynamics of quarks and gluons, it remains a challenge to fully describe the QGP. One way of probing its nature is to study the properties of jets initiated inside the QGP medium with which they will interact at early times, a phenomenon known as Jet-Quenching. The interaction between a jet and the QGP will considerably change the jet's properties and characteristics when compared to jets initiated in the vacuum, such as those happening in proton-proton collisions, making quenched jets an ideal probe into the QGP. The study of quenched jets provides a comprehensive testbed to develop data-driven methods with wide applicability to LHC analyses. Of particular interest, are recent developments of generative methods, such as Generative Adversarial Networks, which can harness the underlying statistical distribution of the data with a lower-dimensional statistical parameterization. In this space, we will be exploring how we can identify the degrees of freedom responsible for the phenomenon of Jet Quenching, and quantify it, which could enable the development of a viable quenched jet tagger. Furthermore we will extend and optimize the techniques as a generic analysis strategy in High Energy Physics that can connect explicitly purely data-driven quantities with theory calculations.
Thermal evolution of hybrid stars
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The compact astrophysical objects, i.e. neutron stars (NSs), hypothetical hybrid (HSs) and quark stars (QSs), are the most dense physical objects accessible by direct observations. Despite the flourishing of astrophysical observations, the internal particle composition of compact stars remains very poorly known. Moreover, the physical processes inside hypothetical objects like HSs and QSs, for which is expected that matter undergoes a phase transition from nuclear matter to a plasma of strongly interacting quarks, are equally poorly understood. This limitation stems from the fact that QCD and its lattice formulation have very limited applicability at large baryonic densities thus not allowing for obtaining a reliable equation of state (EoS). Detection of a QS/HS can become another scientific breakthrough and prove the existence of quark matter, which is the main quest of large research collaborations, such as ALICE at the Large Hadron Collider (LHC) in CERN. Compact stars cool down through a combination of thermal radiation from their surface and neutrino emission from their interior. Observational data of the surface temperature and luminosity of stars provide valuable information about their internal composition, the EoS, the chemical abundances of the envelope and the degree, type and model of pairing of their constituent particles. Studying the thermal evolution of compact objects with a quark core is the primary goal of this research project. Existence of the quark-hadron phase transition, as well as other phase transitions to a denser phase of quark matter, will affect the dynamics of the HS cooling. Their modeling can provide the community with a valuable opportunity to investigate the properties of phase transitions, as well as the EoS of strongly interacting matter at high densities. Finally, this PhD project will also examine the impact of pairing between quarks on the thermal evolution of HS, probing the densest predicted region of the QCD phase diagram.
Muon acceleration in plasma-based acceleration
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Jorge Vieira

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Instituto de Plasmas e Fusão Nuclear -IPFN

Abstract

Plasma-based accelerators may revolutionize science and technology, by bringing more compact, ecological yet powerful accelerators directly into universities and hospitals [tajima&dawson]. A TeV class electron-positron plasma based linear collider is the ultimate goal in the context of high energy physics (HEP). Recent experiments took important steps in this direction, by routinely producing high-quality GeV class electron and positron bunches [berkeley]. As a result of the European strategy for particle physics, Europe is actively considering an alternative approach based on a muon collider. The finite life time of the muon is a challenge for those machines, which need to compensate for muon decay. Plasma accelerators could bring substantial advantages by accelerating muons to relativistic energies before they decay. In this project we plan to investigate, for the first time, muon acceleration in a plasma accelerator. If successful, this work may become a major step towards a plasma-based injector for a future muon collider.
Seeking signatures of dark energy
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Tiago Barreiro

Co-Supervisor: Nelson Nunes

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

This project addresses some of the most important questions in cosmology: Is dark energy accelerating the Universe? What are dark matter and dark energy? Do they interact with each other? How can future missions help addressing these unknowns? The project subtends three different steps: The first consists in the construction of a general class of dark energy theories, not only scalar but also higher spinor, as well as the modification of the geometrical part of Einstein’s equations. It also includes the study of their phenomenology. The second step investigates the linear and non-linear smaller scales, by using both analytical and numerical techniques. These will be put to test against the most up-to-date observational data available. The third step is dedicated to forecast the capabilities that future large surveys have to distinguish between compelling models beyond LCDM. The focus will be Euclid, LISA and ELT-HIRES missions, in all of which the Instituto de Astrofísica (IA) has a strong involvement.
Pulse generator for a scalable discharge plasma source for the AWAKE experiment
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: José Fernando Alves da Silva

Co-Supervisor: Nelson Lopes

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Instituto de Plasmas e Fusão Nuclear -IPFN

Abstract

The PhD program is included in the intermediate and final stages of development of a new plasma source based on direct current discharges on long dielectric tubes filled with rarefied gases (Argon and Xenon), being developed by IST (in collaboration with CERN and Imperial College) for the AWAKE experiment running in CERN. This scalable plasma source will be tested in for the first time in 2022 in electron acceleration experiments using the 400 GeV SPS proton beam (AWAKE Run 2-B - 10 m long plasmas). In the medium term, the more ambitious goal is to add an acceleration section in the AWAKE experiment of at least 50 m by 2027 (AWAKE Run 2-C) based on this technology aiming to demonstrate the scalability of plasma accelerators to energies relevant for HEP. The thesis program is dedicated to the innovative electrical component of the plasma source. Unprecedented uniformity and reproducibility of the plasma density profiles, low cost of construction and operation and low-average-power requirements are achieved by an innovative “ignition + heater” pulsed-power electric circuit developed specially to scale plasma sections to tens of meters and enable the grouping of consecutive plasma sections in series making the plasma length-scalable. In the long term, the technologies developed in this thesis may enable the use TeV hadron beams to produce multi-TeV high quality lepton beam for HEP studies. But the new technologies to ignite and control the temperature of large plasmas in short microsecond short pulses using reliable solid stage-based circuits are relevant to extend new techniques for treatment/elimination of gaseous pollutants (e.g. methane and toxins) to massive industrial use contributing to a cleaner air.
Measurement of Short Range Correlations on Exotic Nuclei at R3B using tRPCs
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Daniel Galaviz Redondo

Co-Supervisor: Alberto Blanco castro

Institution: FCUL (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The goal of the present PhD project is the study for the first time of Short Range Correlations (SRC) in radioactive nuclei. In the framework of the R3B (Reactions with Relativistic Radioactive Beams) experiment of the FAIR laboratory, the candidate will study the high-momentum tail of NN pairs in 16C, the highest N/Z nucleus ever considered, by measuring the breakup reaction of this nuclear system on a proton target in inverse kinematics. The time-of-flight measurement technique will be used to determine the momenta of the relativistic protons emitted in the reaction process, with an improved resolution (about 1%) and a factor of 5 better precision, compared to current technique based on position measurement, thanks to the novelty use of a detector based on Resistive Plate Chambers (RPC). The implementation of the RPC detector as well as the analysis of the measured data will constitute the core of the program, including a 24 month stay at the TU-Darmstadt.
Collider, gravitational and dark relics of Grand Unification with Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Roman Pasechnik

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

This proposal focuses on phenomenological aspects of vector-like fermions (VLFs), leptoquarks (LQs), exotic neutrinos and axion-like particles (ALPs) from the perspective of collider, dark-matter (DM) and Gravitational-Wave (GW) observables. These particles are well motivated by a recently proposed Grand Unified Theory (GUT) [1] and can offer a multi-messenger probe to test the GUT paradigm. We will focus on VLF and LQ signatures at the LHC, with the latter being relevant for RK anomalies, while sterile neutrino and ALP DM candidates can be tested at ALPs-II [2] or XENONnT (www.xenon1t.org/). Phase transitions in the early Universe may result in primordial GW at the reach of LISA or the future Big-Bang-Observer and Einstein-Telescope allowing to probe energy-scales that go from 1 to 10^4 TeV. The development of Machine Learning techniques based on neural networks (NN) and evolutionary algorithms [3] as well as new approaches such as graph NNs and generative models are central to this project and applicable beyond its scope.
Free hyperboloidal evolution in axisymmetry
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Alex Vano-Vinuales

Co-Supervisor: Edgar Gasperin Garcia

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

This thesis project in the field of numerical relativity aims to use compactification methods to tackle General Relativity on hyperboloidal slices, which allow the unambiguous evaluation of global spacetime properties at null infinity. The main objective is a free-evolution hyperboloidal axisymmetric implementation for a commonly used formulation of the Einstein equations. On the way towards the extraction of more accurate gravitational waveforms from the strong field regime, the code will be used to couple gravity to simple matter models, among them fundamental field candidates.
Beyond the Standard Model: interplay between particle and astroparticle physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Filipe Joaquim

Co-Supervisor: Ricardo Gonzalez Felipe

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

The discovery of the Higgs boson at CERN Large Hadron Collider in 2012, provided the last missing piece of the Standard Model (SM) puzzle. The success of the SM lies in its elegant theoretical formulation but notably in its predictive power in remarkable agreement with experimental data. However, the work for particle physicists is still far from over. In fact, the SM fails at explaining the following phenomena: -Neutrino oscillations, which require massive neutrinos and lepton mixing. Due to the absence of right-handed neutrino counterparts, within the SM framework, neutrinos are strictly massless and consequently there is no mixing in the leptonic sector. -The excess of matter over antimatter in the Universe also known as the baryon asymmetry of the Universe, which is underdetermined within the SM. -The existence of dark matter (DM) which composes about 27% of the total amount of matter in the Universe, in comparison visible matter accounts for only 5%. The SM does not provide a viable DM candidate particle. From the theoretical viewpoint, the idea to simultaneously solve the above problems is not only appealing but is also natural since the SM must be the low-energy limit of a more complete theory. From the experimental point of view, the booming worldwide particle physics experimental programme provides very exciting prospects at better understanding the SM and its limitations, probing physics beyond the SM and looking for new physics hints. In line with this, the present PhD programme aims at contributing to the theoretical understanding of the above questions in the framework of theories beyond the SM. Additionally, our research will pay special attention to phenomenological studies and aims at testing SM extensions through confrontation with current and future experimental constraints. To achieve this, we will combine analytical and numerical methods adopted in (astro)particle physics and cosmology.
A next-generation gamma-ray observatory powered by Machine Learning techniques
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Alberto Guillén

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The main goal of this PhD thesis is to develop a next-generation detector concept with Machine Learning (ML) integration, suitable for the ambitious future experiment: the Southern Wide-Field Gamma-ray Observatory aimed to survey the Southern hemisphere sky. The design of a high-performance, cost-effective water Cherenkov detector should be able to cope with the observatory needs, particularly the capability to identify shower muons, essential to ensure an excellent gamma/hadron discrimination. The detector concepts studied in this thesis are based on the placement of multiple light sensors placed at the bottom of the station to explore the signal asymmetries created by the particles crossing it. The complex spatial and time signal structures will be analysed by state-of-the-art Machine learning-based algorithms, allowing to significantly reduce the complexity of the detector and its height. Therefore, this innovative technique would lead to smaller detector units, allowing the experiment to be placed at an extremely high altitude and lowering the energy threshold. These next-generation outdoor detectors with integrated ML techniques pose several challenges ahead, which shall be addressed in this thesis: the complexity of the problem and necessity to perform feature engineering; use of simulations with incomplete accurate descriptions; resilience to spurious effects (backgrounds)... Moreover, the optimisation of the position of the light sensors and the WCD dimensions shall be optimised to maximise the performance and cost of the station. Furthermore, the developed ML methods and detector concept will be used on the shower analysis, particularly the hadronic interaction properties. Such will allow extracting further information from the shower improving the overall observatory sensitivity to astrophysical sources.
Pentaquark spectroscopy for the LHC
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Gernot Eichmann

Co-Supervisor: Teresa Peña

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

In the past two decades there has been tremendous progress in the theoretical and experimental investigation of multiquark states, which has expanded our understanding of what a “hadron” is. Experimental evidence suggests that Nature does not only form conventional mesons and baryons but also more exotic combinations such as tetraquarks and pentaquarks. In particular, there is evidence from LHCb for a number of pentaquark states in the charm-quark mass region. The goal of this project is to shed light on the spectrum and internal composition of such five-quark states with functional methods, which amounts to solving nonperturbative five-body equations in QCD using high-performance computing. This will deliver insight on the mass spectrum of pentaquarks, their resonance poles in the complex plane, their internal quark-gluon structure with possible clustering into meson-baryon pairs, and their size whose knowledge is important for future experiments at the LHC and other facilities.
AutoBSM - Scalable Automation of Beyond the Standard Model (BSM) Physics Validation
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Miguel Crispim Romão

Co-Supervisor: Nuno Castro

Institution: Universidade do Minho

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

As of 2021, the Large Hadron Collider (LHC) has yet to find compelling evidence of New Physics (NP), leaving the High-Energy Physics (HEP) community with a tantalising collection of possible BSM candidate theories to be tested against experimental data. This validation task comprises the search for regions of the parameter space where predictions of the BSM model are in agreement with current experimental data. This involves exploring multidimensional parameter spaces and heavy numerical computations of predictions that are then compared to experimental data. To mitigate the overhead of this step, BSM researchers often simplify their models in order to find viable regions of the parameter space within a reasonable time. This is often done by either simplifying the model, which reduces the dimensionality of the parameter space and the numerical computations involved, or by reducing the constraints on which the BSM model is tested against, effectively increasing the volume of the valid parameter space. In either case, one ends up validating a simplified variation of the BSM model solely due to computational constraints. The student will help develop AutoBSM, a scalable tool for automated BSM physics validation. For this, AutoBSM needs to tackle two challenges in the BSM researchers' workflow: (1) how to efficiently validate a BSM candidate model against experimental data, i.e. how to perform a thorough scan of the parameter space; and (2) how to allow for a platform-agnostic deployment of the code, e.g. on a High Performance Computing (HPC) cluster or in the Worldwide LHC Computing Grid (WLCG). For (1) Machine Learning (ML) algorithms will be used to improve the efficiency of parameter space scanning, reducing the time needed, by orders of magnitude, to find valid regions of the parameter space. For (2) containerised solutions, such as Docker, will be used to deploy such scans in a platform-agnostic way, which will include all the required software dependencies.
Constraining Multi-scalars models with colliders and Dark Matter
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Joao Silva

Co-Supervisor: Jorge Romão

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CFTP - Centro de Física Teórica de Partículas

Abstract

After the observation in 2012 of a new scalar particle closely resembling the Standard Model (SM) Higgs boson, the search for physics beyond the Standard Model (BSM) is now the main goal of the LHC experiments. Extensions of the scalar sector satisfying certain symmetries can provide a natural explanation for Dark Matter (DM) and new sources of CP-violation necessary to fulfil the three Sakharov criteria for baryogenesis. But the analysis of the theoretical constraints and restrictions placed by current data is incomplete for many such models. This project aims to develop theoretical methods to describe multi-scalar models and then confront the phenomenological implications with Higgs, Flavour, and Dark Matter experiments. Particular attention will be given to multi-component DM models. These studies will provide clear predictions and suggestions for future observations and are at the frontier of research.
The effects of dark matter on neutron stars and on their merger dynamics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The merger of two neutron stars (NSs) is one of the most violent events in the Universe and the extreme conditions inside these stars, with densities of about one hundred million tons per cubic centimeter, cannot be tested on Earth. Hence, NSs, in particular the merger of two NSs, provide a perfect laboratory to study matter at its extreme limit. The recent detection of gravitational waves (GWs) consistent with the merger of two NSs, which was accompanied by the observation of electromagnetic signals originating from the same source, marks a breakthrough in the field of multi-messenger astronomy. To relate the observational data to the source properties, one requires accurate theoretical models of the last stages of the binary coalescence. Due to the complexity of the equations governing general relativity and relativistic fluids, this can only be done with advanced numerical relativity simulations. While these simulations have undergone significant improvements in the past, the impact of dark matter (DM) on the binary neutron star (BNS) dynamics has not yet been investigated in detail, despite first studies indicating that DM can cluster around and inside compact objects such as NSs. This research project will investigate these imprints and will provide the first models to fill some of the existing gaps in our search for DM.
Analysis of the asymptotic region of asymptotically flat and de-Sitter like spacetimes
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Edgar Gasperin Garcia

Co-Supervisor: Alex Vano-Vinuales

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The asymptotic properties of spacetimes play a central role in many physical aspects of General Relativity (GR), in particular for the concept of gravitational radiation. One of the crucial concepts introduced for the realisation of the latter, was the use of conformal compactifications introduced in General Relativity by Roger Penrose to describe in a geometric way the notion of infinity. Arguably, the formulation that takes Penrose’s idea of conformal compactification --in conjunction with the theory of partial differential equations and the initial value problem-- to its ultimate consequences are, the so-called, Conformal Einstein Field (CEFE) equations introduced by H. Friedrich in [1]. These equations have been used for analytical purposes such as establishing (semi)-global non-linear stability results de-Sitter and Minkowski spacetimes and some partial global non-linear stability results for black hole spacetimes such as Schwarzschild-de Sitter [2]. Although these equations have been available since 1980 the numerical exploration of spacetimes using the CEFEs is still in its infancy compared with other formulations since they have not been systematically exploited as other formulations of GR. One of the alternatives to the CEFEs to reach the conformal boundary is the use of hyperboloidal foliations and scri-fixing techniques and more standard formulations of the Einstein Field Equations such as the Generalised Harmonic Gauge (EFE-GHG). These have also give fruitful results in combination with the weak null condition ---see [6]--- which can be exploited for numerical implementations [7] and for mathematical analysis [8]. By construction, hyperboloidal foliations reach the null-infinity but stays away from the region close to spatial infinity. The CEFEs on the other hand have access to this region via the construction of the so-called cylinder at spatial infinity. The latter has applications in terms of the calculation of asymptotic charges [4]. These met
Characterization of liquid argon detectors for next generation neutrino physics
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: José Maneira

Co-Supervisor: Fernando Barao

Institution: Universidade de Lisboa

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The question of how neutrinos may be related to the origin of the matter-antimatter asymmetry in the Universe is one of the fundamental goals of Particle Physics today, and the central motivation to accurately measure long baseline neutrino oscillations with the next generation of experiments. The technology of liquid argon time projection chambers (LAr TPCs) allows for massive detectors with excellent tracking and calorimetry -- all crucial capabilities to meet the requirements of the next generation of experiments. In this technique, particles ionize the argon, creating free electrons that drift in an intense electric field and are collected in wire anodes planes, with the measured time providing the drift length. A full characterization of the electric field uniformity and the charge attenuation along the drift are essential to guarantee a precise 3D reconstruction of the neutrino interaction and its energy. This project will be based on the development of calibration and characterization techniques of LAr TPCs with cosmic ray muons, intense UV laser beams, and possibly a dedicated radiation source. It will be focused on the DUNE experiment and its prototype at CERN, ProtoDUNE. New calibration systems will be installed in ProtoDUNE, with the aim of taking data from 2022 onwards. The commissioning and data analysis of ProtoDUNE2 and its calibration systems will be the central part of this work plan, that will conclude with using those results to better estimate the performance of the future DUNE far detector. The candidate will integrate the CERN Neutrino Platform team and will play an active role in the ProtoDUNE2 installation.
The equation of state for compact objects: exploring the effect of strong magnetic fields in the inner crust of neutron stars
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Helena Pais

Co-Supervisor: Francesca Gulminelli

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The first detection of gravitational waves from the merger of two neutron stars in 2017 by LIGO/Virgo set a new exciting multi-messenger era for the astronomy, nuclear, gravitational and astrophysics community. Magnetars, a class of neutron stars that have very strong magnetic fields, are still not very well understood. However, there are already indications that these strong magnetic fields do affect the external layers of these very dense astrophysical objects. This PhD project is dedicated to the construction of a unified equation of state for magnetised stellar matter, which is the essential ingredient to build the stars' mass-radius relation, consistent with recent theoretical, experimental and observational developments. Such equation(s) of state will be made available to the community through the CompOSE repository to be used in core-collapse supernovae and binary neutron star mergers simulations. Special attention will be given to the non-homogeneous equation of state at sub-saturation densities.
Towards a Yoctosecond Imaging tool of the Quark-Gluon Plasma.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Co-Supervisor: Liliana Apolinário

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The main aim of this PhD thesis is to formulate the theoretical and phenomenological framework allowing for experimental measurements of the spatio-temporal evolution of the hot and dense matter created in high energy heavy-ion collisions - the Quark Gluon Plasma (QGP). Jets are abundantly produced in collider experiments and they allow for stringent tests of QCD, given that their evolution spans a wide range of scales - from the initial hard scale of the collision to the hadronic scale at which they are detected. When jets are produced in the presence of a QGP which they propagate through, as in heavy ion collisions, this range of scales allows them to be sensitive to the QGP at different timescales. To endow jets with the ability to probe the time evolution of the QGP, time-ordered momentum- and coordinate-space descriptions of in-QGP jet evolution will be established, an endeavor motivated by the natural space-time reference frame introduced by jet-QGP interactions. Subsequently, a probabilistic implementation of these theoretical descriptions will be pursued, along with its incorporation in existing QGP simulations. The work culminates with the validation of the previous implementation’s outcomes through existing phenomenological tools and subsequent Quantum Chromodynamics-based and Machine Learning aided development of novel observables which can potentiate QGP yoctosecond-resolution tomographical measurements to be explored at the Large Hadron Collider.
Modified gravity: Astrophysical and cosmological applications
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: João Rosa

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Phenomena like inflation, structure formation and late-time cosmic accelerated expansion need further explanation. Although current models favour the existence of dark energy and dark matter, tensions between observational data begin to arise. Modified theories of gravity could resolve these problems. This project aims to explore existing modified theories of gravity, with regard to current and future experimental data, in order to test their viability. This theoretical work will consider generalized scalar-tensor and vector-tensor theories, f(R), f(R,T), and modified Gauss-Bonnet f(G) theories. Brane-world accelerated cosmologies and dynamical dark energy models will also be studied. A successful project would mean uncovering further aspects of these theories, exploring issues of the extra degrees of freedom, and identifying further constraints. It could lead to the rejection of some theories or the proposal of new ones and, ultimately, to better understanding of cosmological data.
New Maps of the Dark Side
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The observational evidence for the acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete. New physics is waiting to be discovered, and forthcoming astrophysical facilities must identify it. The source of acceleration has a low-redshift behaviour akin to a cosmological constant, but current data provides limited information on its high-redshift behaviour and possible interactions. Tackling the dark energy enigma requires extending the redshift range where its behaviour can be mapped. New facilities, such as Euclid, the ELT, and the SKA will enable this, increasing the range and sensitivity of current probes and allowing entirely new tests. This thesis will carry out a systematic exploration of the landscape of physically viable dark energy paradigms and provide optimal discriminating tests. It will focus on Euclid (which the student will join) and broaden to explore synergies and probe combinations with the SKA and ELT-HIRES.

PT-CERN call 2020/1

Results

PT-CERN PhD Grants - Call 2020/1 Final Results for Particle and Astroparticle Physics and associated scientific domains

Following the recommendations of the jury and according to the Terms of the Call, the list of the selected candidates is the following:
ID-004 João Miguel Araújo Vilas Boas *
ID-009 Ivo Arcanjo Jorge Bene Sengo
ID-010 Rodrigo Soares da Graça Antunes Capucha *
ID-018 Ricardo Barrué
*These two candidates decided to not accept the grant.

Results
PT-CERN PhD Grants - Call 2020/1 Final Results for Technologies associated to the Portuguese participation at CERN and their transfer to society

Following the recommendations of the jury and according to the Terms of the Call, the list of the selected candidates is the following:

ID-005 José Miguel Patuleia Venâncio
ID-012 Duarte Guerreiro

Results

Theses (15 theses registered)

Probing particle physics with gravitational waves
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Lara Sousa

Co-Supervisor: Pedro Avelino

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The detection of gravitational waves (GWs) by LIGO ushered in a new era of Astronomy. GWs will allow for the detection of new astronomical sources, enabling us to hear what is currently unseen. This opens the real prospect of detecting cosmic defect networks formed in symmetry-breaking phase transitions in the early universe. We will develop a new generation of numerical algorithms to describe such defect networks, with the objective of gaining new understanding of their evolution and of constructing more realistic semi-analytical descriptions of their dynamics. These tools will enable us to study the GW background and other observational signatures of defect networks with unprecedented precision. Detailed forecasts for upcoming probes (e.g. SKA, LISA,...) and the derivation of observational constraints on defect-forming scenarios will also be central for this project. This work will then give us insight, not only about the early universe, but also about fundamental physics itself.
Black hole shadows, the Kerr hypothesis and fundamental physics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Herdeiro

Co-Supervisor: Pedro Cunha

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

The Event Horizon Telescope (EHT) produced in 2019 the first image of a black hole candidate with resolved horizon scale structure. Imaging the strong gravity region around such compact objects can test the Kerr hypothesis. This hypothesis states that astrophysical black holes are well described by the paradigmatic Kerr solution. In the last few years, new black hole solutions and horizonless compact objects have been proposed considering the interaction with novel ultralight bosonic particles, which can work as a proxy for dark matter. The goal of this project is to study the strong gravitational lensing by this non-Kerr compact objects, using ray tracing codes and General Relativistic Magneto-Hydrodynamic simulations, to obtain images that can be compared with the EHT data. This will constraint models of ultralight bosonic fields and possibly shed new light on the nature of dark matter.
Disentangling and Quantifying Jet-Quenching With Generative Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Co-Supervisor: Miguel Crispim Romão

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At very high energies or densities, quarks and gluons can produce a new state of matter known as Quark-Gluon Plasma (QGP), which is observed in heavy-ion collisions at modern colliders. Due to the non-perturbative nature of Quantum Chromodynamics (QCD), which is responsible for the interactions and dynamics of quarks and gluons, it remains a challenge to fully describe the QGP. One way of probing its nature is to study the properties of jets initiated inside the QGP medium with which they will interact at early times, a phenomenon known as Jet-Quenching. The interaction between a jet and the QGP will considerably change the jet's properties and characteristics when compared to jets initiated in the vacuum, such as those happening in proton-proton collisions, making quenched jets an ideal probe into the QGP. In this thesis, we will explore data-driven methods to explore the characteristics of quenched jets. Of particular interest, we will focus on recent developments of generative methods, such as Generative Adversarial Networks, which can harness the underlying statistical distribution of the data with a lower-dimensional statistical parameterization, called latent space. In this space, we will be exploring how we can identify the degrees of freedom responsible for the phenomenon of Jet Quenching, and quantify it. For this, we will perform a detailed study of how the latent space variables relate to global and substructure jet observables, which are better understood from a QCD perspective, helping us to connect purely data-driven quantities with theoretical efforts.
Effect of dark matter on the nuclear and quark superfluidity inside the compact stars
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ilidio Lopes

Co-Supervisor: Violetta Sagun

Institution: Universidade de Lisboa

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The study of the internal composition of compact stars, such as hybrid stars (HSs), is of primary importance since they seem to be the only natural systems to possess the existence of quark matter and, at the same time, to be able to accumulate a sizeable amount dark matter (DM) in their interior. The research project will include both theoretical and modeling parts. The first one will be dedicated to the analytical formulation of the equation of state (EoS) of strongly interacting matter with the deconfinement phase transition between hadrons and quarks, considering the constraints coming from the astrophysical observations, nuclear matter and the results of quantum chromodynamics on the lattice. By modeling the thermal evolution of HSs, I will implement both the nuclear superfluidity/superconductivity and the quark superfluidity. The effect of DM on the nuclear and quark matter properties will be tested on existing data on compact stars’ cooling.
Thermal evolution of hybrid stars
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The compact astrophysical objects, i.e. neutron stars (NSs), hypothetical hybrid (HS) and quark stars (QSs), are the most dense physical objects accessible by the direct observations. Despite the flourishing of astrophysical observations, the particle composition of the interior of compact stars is still very poorly known. Moreover, the physical processes inside hypothetical objects like HSs and QSs, for which is expected that matter goes through a phase transition from nuclear matter to a plasma of strongly interacting quarks, are also very poorly understood. Particularly, this limitation comes from the fact that QCD and its lattice formulation have very limited applicability at large baryonic densities and as such does not allow to obtain a reliable equation of state (EoS). Detection of QS or HS can become another scientific breakthrough and prove existence of quark matter, which is the main quest of largest research collaborations, such as ALICE at the Large Hadron Collider (LHC) in CERN. Compact stars cool down through a combination of thermal radiation from the surface and neutrino emission from the inner layers. Observational data on the surface temperature and the luminosity of stars provide with the valuable information about their internal composition, the EoS, the chemical abundances of the envelope and the degree, type and model of pairing of their constituent particles. Studying of the thermal evolution of compact objects with the quark core is the primary goal of the present research project. An existence of the quark-hadron phase transition, as well as other phase transition to a more dense phases of quark matter, will have an impact on the dynamics of the HS cooling. Their modeling can provide the community with an important opportunity to probe an existence and properties of phase transitions, as well as the EoS of strongly interacting matter at high densities. Another part of the PhD project will be dedicated to the study of the densest predicted phase on the QCD phase diagram, in which quarks can be paired between each other, and its impact on the thermal evolution of HSs. The thesis will be supervised by Constança Providência and Violetta Sagun, theoretical physicist, in the University of Coimbra
Machine Learning and Measurements of the Higgs boson properties
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Joao Varela

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The subject of this thesis is the search for double Higgs production, decaying into taus and b-jets, at the Large Hadron Collider (LHC). The thesis is placed in the context of the Portuguese participation in the CMS experiment at the LHC, and it is linked to the Beyond the Standard Model (BSM) searches in the more general context of the searches for New Physics processes at the LHC. In the course of the last forty years, the SM has received increasing and consistent verification by precise experimental tests of its predictions, culminating in 2012 with the discovery of a new particle, which appears to be “the” Higgs boson. There are, however, compelling reasons to believe the SM is not complete. In particular, the LIP/CMS group is engaged in the study of SM and BSM processes to fully exploit the opportunities of the unparalleled energy of the LHC collisions. A large amount of data of approximately 150/fb have been collected in Run1+Run2 and are available to study this process. With the upcoming Run3, additional 300/fb of data may become available in the next few years and there will be excellent opportunities for major discoveries in this domain. The work plan includes the study of the double Higgs production, each subsequently decaying to pairs of taus and b-jets. Advanced Machine Learning (ML) techniques will be used in the separation of signal and background events. The candidate is expected to work in a team with a group of researchers. Searches for new physics in this channel can be significantly improved with the additional data, and with improved analysis techniques. The research will be carried out in the context of the Portuguese participation in the CMS experiment at the LHC, in the framework of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”.
Astrophysical and Local Tests of the Einstein Equivalence Principle SUPERVISOR
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The Einstein Equivalence Principle (EEP, which Einstein formulated in 1907) is the cornerstone of General Relativity (only formulated in 1915) but also of the broader class of metric theories of gravity. Although often confused, the two are conceptually distinct, and different experiments probe one or the other. Recent developments, including quantum interferometric tests and dedicated space missions, are dramatically improving the sensitivity of local EEP tests. This thesis will exploit synergies between these local tests and ongoing and planned astrophysical and cosmological tests - some of which also test the EEP, while others only test GR on various scales. We will systematically explore the relevant particle cosmology paradigms (including dynamical dark energy), further constraining them with facilities such as MICROSCOPE and ESPRESSO and also forecasting and planning future contributions expected from Euclid and ELT instruments.
Probing the CP nature of the Yukawa Couplings of the Higgs Boson to Fermions at the LHC
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rui Santos

Co-Supervisor: Antonio Onofre

Institution: FCUL (Universidade de Lisboa)

Host Institution: CFTC - Centro de Física Teórica e Computacional

Abstract

After the discovery of the Higgs boson at the Large Hadron Collider (LHC), particle physicists have turned to the main outstanding issues in particle physics, two of which are: the CP-violation deficit in the Standard Model (SM) and the existence of Dark Matter (DM). Any extension of the SM needs to take these ingredients into account. New sources of CP-violation are needed in order to accommodate the observed predominance of matter over anti-matter in the Universe. Also, if DM comes in the form of a particle, we need to know which are the best candidates. This work focuses on extensions of the SM, designed to find models that match theory with experiment, and their tests at LHC and future colliders. In order to define the best search strategies a close collaboration with the experimental groups at CERN is fundamental to acquire sensitivity to all such models.
Bragg Peak monitoring through prompt-gamma: detection and instrumentation
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Patricia Goncalves

Co-Supervisor: Pedro Assis

Institution: Universidade de Lisboa

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Proton Therapy consists of the irradiation of tumors with a beam of energetic protons. Several advantages arise from the technique, being the main one the minimization of the dose given to health tissues surrounding the mass to be irradiated. In this technique it is common to use a “pencil” beam which can be moved in the XY plane. The protons on the beam will deposit small amounts of energy until they slow down and deposit a large quantity of energy in a limited region - the Bragg peak. The depth of the Bragg peak is closely related to the primary energy and as such it is possible to control the dose also in the z axis. However, other factors can influence the depth of the bragg peak and as such the monitoring of the Bragg peak position is of extreme importance. One of the techniques being considered is to perform the reconstruction of this zone by using prompt-emitted gammas from nuclear reactions of the protons with the tissues. This technique is a subject of dynamic research at LIP to establish the requirements, resolutions and best detectors to monitor the beam Bragg peak. LIP is currently involved in the development of prototypes for the detection of these gamma components. The main requirements is to be able to isolate prompt-gammas, using timing information on the order of the ns scale, and to reconstruct their origin. The current planned detector consists of a collimator to limit orthogonal directions to the beam and a set of particle detectors to sample the position. The instrumentation of the detector will have to deal with a high number of channels and a good timing granularity. However, the energy deposited in the detector may be disregarded and digital channel solutions can be considered. The work will consist of the participation of the simulation effort to understand the expected signals in the detector, the participation in the research prototype irradiation campaigns and the development of the solution for an industrial prototype.
Search for new physics in exclusive processes at the Large Hadron Collider.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Jonathan Hollar

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The subject of this thesis is the search for New Physics in exclusive processes at the Large Hadron Collider (LHC). Production of exclusive processes occurs with high cross section in gamma-mediated processes at the LHC. Photon-photon collisions may provide the conditions to study particle production with masses at the electroweak scale. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to select exclusive processes and probe the standard model. PPS is a detector system at approximately 210 m from the interaction point around the CMS detector, and it is designed to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive processes. Since 2016, PPS has been taking data in normal high-luminosity proton-proton LHC collisions. The goal of this research project is to select and identify for the first time in data the extremely rare processes of heavy particles – including top quarks and W bosons - produced exclusively and identified with proton tagging. The research will be carried out in the context of the Portuguese participation in the CMS experiment at the LHC in the more general context of the searches for New Physics processes at the LHC, in the framework of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”. The candidate is expected to work in a team with a group of researchers.
Testing modified gravity with black holes
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Jorge Rocha

Co-Supervisor: Daniele Vernieri

Institution: Universidade de Lisboa

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

Extensions of General Relativity (GR) appear to be inescapable in order to consistently combine gravitational and quantum physics, and to explain the observed cosmological evolution. Black Holes (BHs), where gravity is strongest, are an ideal testbed to scrutinize such theories. Modifications of GR leave imprints, essential to be quantified, in gravitational wave signals. In this respect, only few alternative theories of gravity have been considered so far. My research plan is focused on the study of some theoretical aspects of BHs Physics in modified theories of gravitation, such as Horndeski theory, Hořava gravity and Einsteinian cubic gravity. In the framework of these well-motivated and viable theories, on one hand I will consider the fusion of BHs, in order to obtain some analytical results about the geometry of the event horizon and its time dependence. On the other hand, I will evaluate BHs tidal deformabilities computing their tidal Love numbers.
Scintillating array for real-time high-resolution ion therapy dosimetry
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Jorge Sampaio

Co-Supervisor: Luis Peralta

Institution: FCUL (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Radiobiological effects depend strongly on the track-structure of particles crossing the tissues. The clustering of energy deposition determines the degree of cell damage and the ability of cells to repair. Thus, an important component of radiobiology experiments is the measurement of doses with high spatial resolution and as close as possible to the irradiation conditions of the irradiated tissues. The objective of the project is to develop a detector prototype that combines tissue-equivalence, the unique capability to support cell growth, real-time dose measurements with high spatial resolution, and cost-effectiveness. The detector will be constructed of juxtaposed thin plastic scintillating fibers coupled with a system for reading and converting the optical signal into deposited energy. The project involves tasks of design and construction of the detector and associated electronics, simulations of the detector's response to proton and heavy-ion radiation fields, tests, and calibrations of the detector with radioactive sources and particle beams. The Ph.D. student will be integrated into a team with extensive experience in the development of detectors based on scintillating fibers and in Monte Carlo simulations. The work will be carried out in national and international collaborations with biology research laboratories and particle accelerator facilities.
Search for New Physics in the associated production channel of a Higgs and a W boson at ATLAS
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Patricia Conde Muino

Co-Supervisor: Rui Santos

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The main objective of this research plan is to measure the Spin and CP properties of the interaction vertex between the Higgs and the W bosons (hWW vertex). The measurement will be done using the proton-proton collisions recorded by the ATLAS Collaboration during the LHC Run 1 and Run 2, as well as the data to be collected in the Run 3. Therefore, as second objective of this research plan, a contribution to the ATLAS data taking and detector operations programme is foreseen, with a focus on the ATLAS jet trigger system.
Four-dimensional regularization tools for precision calculations in and beyond the Standard Model
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Brigitte Hiller

Co-Supervisor: Adriano Cherchiglia

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The data collected and analysed at the LHC do not point to significant deviations from the Standard Model (SM), yet some open questions remain unanswered such as dark mass, dark energy, baryon asymmetry, Higgs mass fine tuning, strong CP problem. To distinguish background (SM) from possible new contributions, it is paramount to develop stringent tests of self consistency of the SM. In this context, the calculation of cross sections beyond leading order in perturbation theory is a vital ingredient to allow comparison with experimental data provided by particle colliders. Whilst computations at next-to-leading order (NLO) are standard, it is well known that next to next leading order (N2LO) and subsequent N3LO calculations demand sophisticated theoretical and computational strategies, relying heavily on regularization and renormalization schemes. It is argued that Implicit Regularization is an ideal framework to implement some important processes in the SM and beyond, analysed in this proposal.
Causality in Lorentzian CFT’s
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Miguel Costa

Co-Supervisor: Vasco David Fonseca Gonçalves

Institution: Universidade do Porto

Host Institution: CF-UM-UP - Centro de Física das Universidades do Minho e do Porto

Abstract

Our current understanding of fundamental interactions is based on the universal language of Quantum Field theory (QFT), which describes the Standard Model, gravity, early universe inflation, as well as many condensed matter phenomena. Under the renormalisation group flow QFT’s are usually defined starting from a free Conformal Field Theory (CFT) in the UV that flows to another non-perturbative CFT fixed point in the IR or to a gapped phase. In addition, CFT’s define a dual gravity theory in Anti-de Sitter (AdS) space [1], becoming a tool to uncover the secrets of quantum gravity. These reasons explain why CFT’s are of primary importance in theoretical physics. This thesis proposes to study CFT’s using modern non-perturbative bootstrap techniques [2]. Our main focus will be on understanding the properties of Euclidean CFT’s that define causal Lorentzian theories, as well as unitary evolution in the dual AdS gravity theory.

PT-CERN Call 2020/2

Results

PT-CERN PhD Grants - Call 2020/2 Final Results for Technologies associated to the Portuguese participation at CERN and their transfer to society

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:
ID-024 Miguel Molina
ID-023 Rudnei Machado

Results
PT-CERN PhD Grants - Call 2020/2 Final Results for Particle and Astroparticle Physics and associated scientific domains

According to the recommendations of the jury and to the Terms of the Call, the list of the selected candidates is the following:
ID-003 Matteo Pisano
ID-010 Matteo Piani
ID-018 Maura Gabriela BarrosTeixeira
ID-005 Paulo Bernardo Ferraz
ID-015 João Diogo de Freitas Dias
ID-013 Joan Bachs Esteban

Results

Theses (21 theses registered)

Radiation Damage of the TileCal Optics components at the High Luminosity LHC phase
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Rute Pedro

Co-Supervisor: Patricia Conde Muino

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The ATLAS Tile Calorimeter (TileCal) is an essential instrument to measure jets, hadronic tau decays and the missing energy, participating in the trigger and providing decisive information for electron/photon identification. The organic scintillators and wavelengthshifting fibres of the detector are known to degrade with LHC operation, which will be extended by the High-Luminosity LHC phase. The objective of this research plan is to study the impact of radiation damage into the performance of TileCal measurements such as jets, electrons/photons or others, to timely diagnose the need for dedicated mitigation strategies. Current lower limits on the optical detector response will be used to simulate future scenarios and, e.g., the jet energy resolution will be determined and employed as a performance metric. Laboratory irradiations of scintillators and wavelength-shifter fibres will be carried on. The irradiated materials will be characterised at LIP’s Laboratory of Optics and Scintillating Materials (LOMaC) for their radiation damage profile in terms of dose rate and geometric properties. These complementary data is expected to give useful input to the simulation model. Moreover, the TileCal performance history with dose exposure together with laboratory data on radiation hardness of TileCal’s components is a very useful and timely input to the design of future collider experiments.
Birds of a feather: seeking the earliest high-energy events in the Universe at the high- and low-energy ends of the spectrum
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Afonso

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The existence of powerful Active Galactic Nuclei (AGN) has now been established well within the first Gyr of the Universe, through the observations of tens of optically or near-infrared selected Quasi Stellar Objects (QSOs) up to the currently highest redshift of z ∼ 8. Theoretical work has been developed showing how super-massive (M∼ 109 M⊙) black holes can exist at such early epochs, depending on the unknown but necessarily quick assembly and growth from a suitable seed. To understand what are these supermassive black holes (SMBH) seeds, how they lead to early AGN activity and how relevant this is to the early galaxy and structure formation, it is fundamental to detect AGN activity at the highest redshifts, well within the Epoch of Reionisation. Surprisingly, the sensitivity already exists to find such sources at both extremes of the electromagnetic spectrum, X-rays and radio wavelengths, but all efforts to detect them have so far been unsuccessful. This is presumably due to their expected rareness, but certainly also due to the lack of understanding of the high-energy physical processes present in these youngest extreme sources in the Universe. While wide area surveys to be performed with future telescopes such as Athena (in the x-rays) and SKA (in the radio) will overcome the former limitation, the latter suggests correct identification of such ”rosetta stone” sources will remain challenging, as we are unable to optimise our observations and detection strategies to these sources. Taking advantage of the strong Portuguese participation in these two future international observatories, this PhD project will explore the synergies allowed by the combination of the unique capabilities of Athena and SKA for the exploitation of the earliest AGN activity. Following-up on our recent work (Amarantidis+2019), the student will explore state-of-the-art galaxy and SMBH formation and evolution models, analyse the physical processes they assume, and implement new recipes for X-ray and radio emission processes - taking into account the most recent advances in our understanding of black hole accretion physics. This will lead to improved methodologies for the selection of very high redshift AGN, which will be tested in current deep X-ray and radio surveys. Finally, such methodologies will be used to optimise Athena and SKA observing strategies for the detection of the earliest examples of AGN activity.
Machine-Learned Statistical Inference on Cosmological Survey Data
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Andrew Liddle

Co-Supervisor: Antonio da Silva

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The overall objective is the development, implementation and deployment of novel algorithms for statistical analysis of large cosmological survey datasets, with particular emphasis on machine/deep learning innovations emerging in the literature. We propose the application of state-of-the-art machine-learning techniques to address the following most pressing topics of modern cosmology, via model-level and model-independent inferences. One initial direction will be the development of machine-learned sampling for Bayesian evidence calculations in cases where likelihood evaluations are extremely costly, as is increasingly becoming the case with large-scale structure data. A second direction is the use of symbolic regression to seek model-independent information on Dark Matter, Dark Energy and Inflation directly from survey data, building on the work of Schmidt, Udresco, Tegmark and others [SCHMIDT, UDRESCO, LIU]. A third direction is to use the obtained results and developed pipelines to address the tensions [LAHAV] between: 1. Measurements of the Hubble constant (Planck vs. SH0ES + H0licow datasets) via early and late Universe probes: 4 to 5 sigma mismatch; 2. Measurements of the amplitude of perturbations via CMB radiation and matter power spectra (Planck vs. DES + KiDS): 2 to 3 sigma mismatch; A considerable degree of a-priori model assumption / bootstrapping is employed in existing analyses. We will use our model-independent approach to reconcile the different datasets, and further limit the model parameter space in order to shed light on the nature of Dark Matter, Dark Energy and Inflation.
Collider, neutrino and dark relics of Grand Unification with Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Felipe Ferreira de Freitas

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

The last decade witnessed the confirmation of three outstanding milestones in fundamental physics recognized with the attribution of three Noble Prizes. In 2013, such an award was granted to the Higgs boson discovery dated from 2012 thus completing the Standard Model (SM) of Particle Physics. 2017 was the year of conceding the Nobel Prize to the discovery of Gravitational Waves in 2015, 100 years after Einstein has published his theory of General Relativity. Last but not least, 2015 was also the year where the discovery of neutrino flavour oscillations in 2002 was rewarded with a Nobel Prize. The latter discovery is one of the strongest evidences that the SM is by no means a complete description of particles and interactions. In fact, flavour oscillations between different neutrino species imply a quantum superposition of mass eigenstates which the SM cannot offer. Furthermore, the existence of dark matter (DM), from galaxy rotation curves and anisotropies in the Cosmic Microwave Background is becoming increasingly favoured by a particle physics explanation that is absent in the SM. With this thesis we aim at exploring both the DM and neutrino mass problems focusing on a novel trinification Grand Unified Theory (T-GUT) supplemented with a local family symmetry. Besides the unification of forces, this high-scale theory also features the unification of the Higgs and matter sectors. Therefore, the existence of a large unified representation yields a rich neutrino sector at the low-scale containing 9 Dirac weakly interacting components, of which 3 are sub-eV, and 6 heavy Majorana ones. One of the key studies proposed to develop in this thesis is to understand which regions of the parameter space allow for a Pontecorvo–Maki–Nakagawa–Sakata (PMNS) mixing and which implications it poses to the high-scale theory. Furthermore, the lightest Majorana neutrino can be sterile enough to provide a potential candidate for the DM. The new Dirac-type heavy neutrinos are accompanied by three generations of vector-like leptons offering an interesting opportunity for collider searches and phenomenological studies at the Large Hadron Collider. The low energy limit of the T-GUT framework also offers 2, down-type, singlet vector-like quarks (VLQ) not far from the TeV scale and at the reach of the LHC or future colliders. Furthermore, it follows from the unification picture that the mass spectrum of such vector-like fermions are directly related to the ultra-violet limit of the model and a potential discovery could be regarded as a relic of a more fundamental theory. The techniques we aim to develop in order to address the above questions will involve optimization algorithms based on Evolutionary searches for Deep Learning and Machine Learning tools. As a novel application, we intend to use such techniques as a “control” environment for Monte-Carlo event generator software, such as e.g. MadGraph, Pythia or MicrOmegas, in combination with model building tools such as SARAH and Feynrules. These studies also involve the development of algorithms based on probabilistic programming language and Bayesian Deep Learning. Such techniques will be used as a generative model environment, allowing us o make Monte-Carlo event generators to work in a more efficient ways by looking for model parameter space points consistent with both theory and experimental data. Last but not least, such tools will be built following a model-independent philosophy in order to promptly apply them to different New Physics models.
Thermal evolution of hybrid stars
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The compact astrophysical objects, i.e. neutron stars (NSs), hypothetical hybrid (HSs) and quark stars (QSs), are the most dense physical objects accessible by direct observations. Despite the flourishing of astrophysical observations, the particle composition of the interior of compact stars is still very poorly known. Moreover, the physical processes inside hypothetical objects like HSs and QSs, for which is expected that matter goes through a phase transition from nuclear matter to a plasma of strongly interacting quarks, are also very poorly understood. Particularly, this limitation comes from the fact that QCD and its lattice formulation have very limited applicability at large baryonic densities and as such does not allow to obtain a reliable equation of state (EoS). Detection of QS or HS can become another scientific breakthrough and prove the existence of quark matter, which is the main quest of largest research collaborations, such as ALICE at the Large Hadron Collider (LHC) in CERN. Compact stars cool down through a combination of thermal radiation from the surface and neutrino emission from the inner layers. Observational data on the surface temperature and the luminosity of stars provide valuable information about their internal composition, the EoS, the chemical abundances of the envelope and the degree, type and model of pairing of their constituent particles. Studying of the thermal evolution of compact objects with a quark core is the primary goal of the present research project. Existence of the quark-hadron phase transition, as well as other phase transitions to a denser phase of quark matter, will have an impact on the dynamics of the HS cooling. Their modeling can provide the community with an important opportunity to probe the existence and properties of phase transitions, as well as the EoS of strongly interacting matter at high densities. Another part of the PhD project will be dedicated to the study of the densest predicted phase on the QCD phase diagram, in which quarks can be paired between each other, and its impact on the thermal evolution of HSs. The thesis will be supervised by Constança Providência and Violetta Sagun, theoretical physicists, in the University of Coimbra.
Simulation inference and generative artificial intelligence for the next era of fundamental physics from observational cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Andrew Liddle

Co-Supervisor: Antonio da Silva

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

The overall objective of this project is development, implementation and deployment of novel algorithms for statistical analysis of large cosmological survey datasets, with particular emphasis on machine/deep learning innovations emerging in the literature. These include, but are not limited to; generative models, Bayesian neural networks, intelligent sampling algorithms, and model-independent inference. The application of methods in the emergent literature of artificial intelligence are likely to be amongst the first of their kind in cosmology and physics. The unique power of these machine learning techniques ensures a conclusive and precise search into the future tenets of cosmology. By exploiting the supervisors’ roles in the ongoing Dark Energy Survey and the upcoming Euclid satellite -- co-supervisor António da Silva is the Portuguese lead investigator for Euclid -- we will access state-of-the-art data to target specific science goals, including the nature of primordial perturbations in the Universe and the properties of the neutrino sector. Using innovations brought to the field by artificial intelligence, together with the deep field Euclid observations, the project aims to disseminate advances from understanding early Universe perturbations, exotic cosmologies, theories of gravity and fundamental physics. These investigations, trialled on the Dark Energy Survey, will benefit and shape the understanding of our Universe as informed by the forthcoming Euclid satellite data.
Astrophysical and Local Tests of the Einstein Equivalence Principle
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

The Standard Model of particle physics is one of the most well succeeded theories known to physicists. It has endured a number of tests proving to be resilient and experimentally accurate theory. However, there are several reasons that lead physicists believe that this theory is still lacking something. For this reason, theories beyond the SM are being explored. Some of these theories lead to remarkable consequences, such as predicting violations of the Einstein equivalence principle. The Einstein Equivalence Principle (EEP, which Einstein formulated in 1907) is the cornerstone of General Relativity (only formulated in 1915) but also of a broader class known as metric theories of gravity. Recent developments, including quantum interferometric tests and dedicated space missions, promise to revolutionize the field of local tests of the EEP and dramatically improve their current sensitivity. This thesis will explore new synergies between these imminent new local tests of the EEP and ongoing or planned astrophysical and cosmological tests: some of these directly test the EEP, while others only test GR on various scales. We will explore relevant paradigms (including string theory and scenarios with and without screening mechanisms), develop a taxonomy for various model classes, and study how they are further constrained by experiments such as MICROSCOPE and ACES, in combination with astrophysical data from ESPRESSO, ALMA and other facilities. The work will also be directly relevant for the science case of several ELT instruments, as well as Euclid and the SKA.
The electroweak vacuum and di-Higgs production at the LHC
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ricardo Gonçalo

Co-Supervisor: Konstantinos Nikolopoulos

Institution: Universidade de Coimbra

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Since its discovery, the Higgs boson became a prime tool to search for physics beyond the Standard Model (SM). At the current level of precision, the Higgs boson is compatible with SM expectations. A number of open questions suggest the existence of new physics, that could be unveiled as we explore the LHC data. A wealth of experimental results from the ATLAS and CMS experiments, probe the region around the minimum of the Higgs potential, or vacuum. But the shape of this potential is not constrained experimentally. This shape is intimately connected to the breaking of the electroweak gauge symmetry, which resulted in the fundamental forces we experience today. To experimentally constrain this shape we must measure the Higgs boson selfcoupling, which is accessible at the LHC through the simultaneous production of two Higgs bosons. The selected student will join the Portuguese ATLAS team, working in close collaboration with theorists and integrated into our international collaboration. He or she will be able to contribute to enhancing our current knowledge in this important area, which will become one of the most important measurements of LHC experiments. The student will also employ the latest theory developments and the most recent advances in reconstruction techniques: from boosted object identification to machine learning. Part of this research will be done at the University of Birmingham, in the United Kingdom, in co-supervision with a colleague from the ATLAS collaboration. The successful student will be able to participate in the operation of the ATLAS experiment during the LHC Run 3 to start in 2021, and travel to CERN will be required.
Collapsed structures in scalar-tensor theories of gravity
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Javier Rubio

Co-Supervisor: Ilidio Lopes

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

Many beyond the Standard Model theories introduce novel scalar degrees of freedom in order to explain inflation, dark energy and dark matter. Interestingly enough, these fields could play an important role not only on the dynamics of the Universe as a whole but also on the evolution of collapsed structures such as galaxies or stars. In particular, the presence of additional scalar degrees of freedom gives rise, almost generically, to new attractive forces able to modify the standard gravitational collapse of General Relativity. Depending on the precise couplings to matter, this modification could allow for unexpected phenomena such as the formation of primordial black holes during radiation domination or the existence of neutron stars with scalar hairs on spherically symmetric backgrounds. This PhD thesis focuses on the role of scalar interactions on the formation and evolution of compact structures in the early and late Universe. By using analytical and numerical techniques, we will study aspects such as the dynamical development of the screening mechanism, the formation and stability of structures with scalar hair and the impact of fifth forces on the formation and evolution of stars. In particular, we are interested in models involving universal and non-universal couplings to the visible and dark matter sectors. Our studies could have a strong impact on our understanding of the relation between dark energy and dark matter while being relevant for current and future astrophysical and cosmological surveys such as GAIA.
Machine Learning approaches for Gravitational-Wave Astronomy: data analysis and detection
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio Onofre

Institution: Universidade do Minho

Host Institution: CF-UM-UP - Centro de Física das Universidades do Minho e do Porto

Abstract

The first detection of a gravitational wave (GW) signal in 2015, generated by the merger of two black holes (BHs), opened an entirely new way to understand the cosmos [1] unveiling a previously unknown population of massive stellar BHs and enabling the first tests of General Relativity (GR) in the strong-field regime. In 2017, the first observation of a binary neutron star (BNS) merger by the LIGO and Virgo detectors opened the era of multi-messenger astronomical observations [2]. With the unprecedented coordinated action of the LIGO Scientific Collaboration (LSC), the Virgo Collaboration, and dozens of astronomical facilities, key evidence to address open issues in relativistic astrophysics was collected [3]. The evolution of the kilonova phenomenon has been studied in detail [4,5] and GW observations of the event have constrained the equation of state of neutron stars (NS) [6]. The combination of the electromagnetic (EM) and GW observations has also opened the field of GW cosmology with a new way to measure the Hubble constant [7]. Searches of neutrino counterparts of GW events are also carried out routinely, but have not yet led to a detection [8]. Moreover, during the last observational campaign of the LIGO-Virgo detectors, O3, GW candidate events have been released as public alerts to facilitate the rapid identification of EM or neutrino counterparts, expanding the capabilities of multi-messenger astronomy. A significant number of candidates have been publicly announced on the GW candidate event database (gracedb.ligo.org) and some confirmed detections have already been published [9-13], increasing the number of detections from the first two observing runs [14].
The effects of dark matter on neutron stars and on their merger dynamics
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

The merger of two neutron stars (NSs) is one of the most violent events in the Universe and theextreme conditions inside these stars, with densities of about one hundred million tons per cubiccentimeter, cannot be tested on Earth. Hence, NSs, in particular the merger of two NSs, providea perfect laboratory to study matter at its extreme limit.The recent detection of gravitational waves (GWs) consistent with the merger of two NSs, whichwas accompanied by the observation of electromagnetic signals originating from the same source,marks a breakthrough in the field of multi-messenger astronomy. To relate the observational datato the source properties, one requires accurate theoretical models of the last stages of the binarycoalescence. Due to the complexity of the equations governing general relativity and relativisticfluids, this can only be done with advanced numerical relativity simulations. While these simula-tions have undergone significant improvements in the past, the impact of dark matter (DM) on thebinary neutron star (BNS) dynamics has not yet been investigated in detail, despite first studiesindicating that DM can cluster around and inside compact objects such as NSs. This research project will investigate these imprints and will provide the first models to fill some of the existing gaps in our search for DM.
Collider and Gravitational probes for New Physics in Multi-Higgs Models
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: António Morais

Co-Supervisor: Felipe Ferreira de Freitas

Institution: Universidade de Aveiro

Host Institution: CIDMA - Centro de Investigação em Matemática e Aplicações da Universidade de Aveiro

Abstract

With the recent observation of gravitational waves (GW) by the LIGO-VIRGO collaboration and the Large Hadron Collider (LHC) RUN-3 scheduled to start at the middle of 2021 with twice the nominal luminosity and a center of mass energy of 14 TeV, a great opportunity for New Physics searches following a multi-messenger philosophy has emerged. In particular, models with extended scalar sectors feature the possibility of first order phase transitions (PT) capable of generating a stochastic background of primordial GW which, if detected, can become a gravitational portal and a probe for Beyond the Standard Model (BSM) physics. The LISA mission will offer a range of frequencies well into the mHz region, relevant for the electroweak (EW) PT. The non-trivial structure of such extended scalar sectors allows for multi-step phase transitions and corresponding GW signatures. This information, in synergy with collider physics, can offer complementary information on the quest for hints of a more complete description of particles and interactions. In this thesis we will consider models with additional electroweak Higgs doublets and singlets, supplemented by additional flavour or gauge symmetries, whose breaking takes place not far from the EW scale. We will investigate which particular BSM signatures are expected at the LHC for different benchmark models and how can this information be complemented by the stochastic background of GW, with focus on the future LISA mission. We will also consider models where vector-like fermions, extended neutrino sectors as well as composite Higgs scenarios will be studied along the same research strategy. These studies involve the development of intelligent algorithms based on Evolutionary searches for Deep Learning and Model Agnostic Meta-Learning (MAML). Such techniques can be used as a “control” environment for Monte-Carlo event generator software tools, such as MadGraph, Pythia and CosmoTransitions. One consequence of using these techniques is the possibility to accelerate the task of simulating data points for a given specific model. Simulations provided by MadGraph, Pythia and CosmoTransitions are rather CPU intensive and demand a fair amount of time to provide a significant statistics. One possible way to speed up the computation is to use Deep learning techniques, such as MAML, in order to capture the underlying features inherent of a given BSM scenario while leveraging such features to sample points more efficiently.
Evaluating the Effectiveness of Mini-Beam Radiation in Cancer Therapy
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Patricia Goncalves

Co-Supervisor: Joao Seco

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Technological developments play an important role in the improvement of cancer therapy. Radiation-therapy is, in particular, a rapidly evolving field and it is used as a form of treatment for as many as half of the cancer patients [1]. The refinement of the treatment techniques improved patient care and led to an increase in the survival rate. Long term survivors are the ones who potentially benefit the most from the developments aiming to reduce the side effects of radiation-therapy. The most commonly chosen approach to affect the lesions without inducing side effects is improving the conformality of the dose delivery. In general, the approaches adopted in clinical practice aim to achieve tumor control by delivering a uniform dose to the target volume. In pre-clinical studies several other options have been investigated, which not always base their rationale on uniform dose distributions and conformality [2]. A prominent case is the micro- and mini-beam radiation therapy (MBRT), where a spatial pattern of high-dose beamlets alternates with low-dose valleys. This has been investigated in animal experiments with photon beams (MRT) at synchrotron facilities with photons and at cyclotron facilities with protons. MBRT has been investigated at two different spatial scales in the literature at the micrometer and millimeter scale. In both cases, the setup utilizes arrays of parallel thin radiation planes separated by short distances. In first approximation, along the transverse profile, the radiation can be modeled by a series of m equidistant rectangular peaks separated by valleys without direct delivery of the beam. The Goals of this thesis are to investigate how spatially fractionated mini-beams produce effectively tumor control; to perform Monte Carlo inter-comparison for chemical reactions present in codes such as TOPAS-nBIO, GEANT-DNA and gMicroMC and to establish which Monte Carlo is best suited for the description of spatially fractionated mini-beams.
Coding the Cosmos: Simulating Superstrings in the GPU Era
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Institution: Universidade do Porto

Host Institution: Centro de Astrofísica da Universidade do Porto

Abstract

Cosmic strings arise naturally in many proposed new physics beyond the standard model such as Grand Unified Theories, inflation and even string theory. This has obvious benefices since most of new physics require such high energies that are currently unavailable at current accelerators and Cosmic strings offer a new window into the early Universe that could be tested with current and next-generation facilities such as CORE and LISA. However, there is a bottleneck in the lack of accurate high-resolution simulations of defect networks that can be used as templates for robust statistical analysis. Most numerical simulations so far have been performed for the simplest Abelian-Higgs (or Nambu-Goto) model while realistic cosmic strings are expected to have non-trivial internal structure, includng charges and currents. The scientific goal of the thesis is to fill this gap. This thesis will continue the development of a new generation of high-scalability defect evolution codes that will match the sensitivity of ongoing and forthcoming observational searches.
Searching for dark matter with the ATLAS detector using unconventional signatures
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Castro

Co-Supervisor: Marek Tasevsky

Institution: Universidade do Minho

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

Although we have a wealth of evidence for the existence of dark matter, its nature is still a complete mystery which collider data can take an important role in uncovering. For this, the LHC collaborations have developed a comprehensive search programme for dark matter signatures, mostly based on X in addition to missing transverse energy topologies, with X being a gauge boson, a Higgs or jets. The current proposal aims at exploring for rare dark matter signatures by tagging either a top quark plus missing energy, the monotop signature, or pairs of soft leptons with scattered protons tagged at very small polar angles. The monotop signatures can be a powerful probe of specific dark matter signals appearing in models involving preferential couplings beyond the Standard Model to the top quark. Such signatures rely on the tagging of a highly boosted top quark, together with significant amounts of missing transverse energy. Proper modelling of the expected backgrounds, as well as advanced machine learning techniques, will be explored to enhance the expected sensitivity of this search, allowing to fully benefit from the ATLAS dataset to be collected during the third operation phase of the LHC. Close collaboration with the theory community will be pursued, allowing to explore the phenomenological implications of the obtained results. Complementary to this search, the current proposal also targets another rare signature, where the two scattered LHC protons emit two photons that annihilate to produce a pair of sleptons, which are particles used by theories beyond Standard Model, that decay into two neutralinos and two soft leptons, with the neutralinos being candidates for particles of Dark Matter. The protons, which stay intact after the interaction, are scattered through very small angles and can be detected with the ATLAS Forward Proton tagging detectors (AFP), effectively converting the LHC into a photon-photon collider. Since there is no underlying event, the two leptons are the only particles produced centrally. The invariant mass of the particles produced centrally can be measured precisely by determining the proton energy loss with the AFP detectors, even in the case of neutrinos in the final state. The tagging of the protons can provide a way of triggering signatures where the leptons are too soft to be triggered by themselves. This final state can be used to search for dark matter in photon-induced processes, using also the capability of the forward proton tagging detectors. Given the novelty of such searches in this setting, machine learning algorithms with the capacity of detecting generic new physics candidates will be developed. Such search for dark matter is challenging due to the low transverse momentum of the leptons produced. An adequate strategy for triggering this kind of processes is therefore needed. It implies the combination of proton tagging information with muon/electron triggers reconstructed with the ATLAS central detectors, already at the first level trigger and probably making use of the topological trigger processors. The development and optimisation of such a trigger strategy is also an objective of this project. The student will develop the work in the framework of the ATLAS international collaboration, and will be integrated in the ATLAS Portuguese Group, in close collaboration with the Institute of Physics of the Czech Academy of Sciences. The candidate will also contribute to the ATLAS data taking activities and to the commissioning and performance studies of the AFP detector, fundamental for the success of this project. Frequent presentations to the Collaboration of the results achieved are expected and the obtained results will lead to different publications in reference journals and presentations in international conferences and workshops.
Particle production in inflationary cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: João Rosa

Co-Supervisor: Roberto Vega-Morales

Institution: Universidade de Coimbra

Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra

Abstract

In this research proposal the candidate will explore inflationary models of the early universe where the effects of interactions between the inflaton and other fields present in the cosmic plasma play a crucial role. These effects lead to warm inflation scenarios and to dark matter production mechanisms. The aim of this research proposal is then to incorporate these mechanisms into concrete particle physics frameworks and to investigate the impact that they may have on the cosmic history, analysing in particular the production of dark matter and baryon asymmetries, thermal effects on the dynamics of the inflaton field and radiation perturbations and the associated observational and laboratory signatures. The candidate will conduct research at both the University of Coimbra, Portugal, and the University of Granada, Spain.
A next-generation gamma-ray observatory powered by machine learning techniques
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Alberto Guillén

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The observation of the high-energy gamma-rays provides a unique window to explore the extreme energy universe and fundamental phenomena related to it. The observation of these rare phenomena implies the construction of huge compact experiments, with areas of 1 km^2, placed at altitudes that surpass the 5000 meters above sea level. These experiments should be able to fight the enormous hadronic background to observe the gamma-rays. Classically, this has been done by identifying muons, which led to detector options which are unfit for such an ambitious project. New ideas to build a next-generation experiment are currently being assessed by the Southern Wide-field Gamma-ray (SWGO) collaboration. At LIP, we have shown that the application of Machine Learning algorithms together with innovative detector solutions, can lead to a smaller, more capable next-generation detector which could revolutionize the field of gamma-rays. In particular, the time evolution of the detector response can be exploited to identify the nature of the particle entering the tank. While very promising, the implementation of these neural networks has many challenges ahead: the complexity of the problem and necessity to perform features engineering; use of simulations with incomplete accurate descriptions; resilience to spurious effects (backgrounds)... This work will be developed in close collaboration with the Computer Technology and Architecture department of Granada University.
Inflation, the Standard Model Higgs and the nature of gravity
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Javier Rubio

Co-Supervisor: Ilidio Lopes

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: CENTRA - Center for astrophysics and gravitation

Abstract

The properties of the recently discovered Higgs boson together with the absence of new physics at the Large Hadron Collider (LHC) allows us to speculate about consistently extending the Standard Model (SM) all the way up to the Planck scale while staying in the perturbative regime. In this context, the SM Higgs non-minimally coupled to gravity could be responsible for the symmetry properties of the Universe at large scales and the generation of the primordial spectrum of temperature fluctuations seen in the Cosmic Microwave Background (CMB). Interestingly enough, the detailed predictions of this general paradigm are sensitive to the different incarnations of gravity, opening the door to test its fundamental nature with collider experiments and future cosmological probes such as the Simon Observatory or LiteBIRD. This thesis will carry out a systematic exploration of the relation between the Higgs field and gravity. In particular, we will attempt to identify a set of self-consistent Einstein-Cartan theories able to describe the whole evolution of the Universe in the absence of new degrees of freedom above the electroweak scale. To this end, we will follow a multidisciplinary approach combining theoretical and particle physics requirements such as unitarity and radiative stability with cosmological and astrophysical observations.
Disentangling and Quantifying Jet-Quenching With Generative Deep Learning
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

At very high energies or densities, quarks and gluons can produce a new state of matter known as Quark-Gluon Plasma (QGP), which is observed in heavy-ion collisions at modern colliders. Due to the non-perturbative nature of Quantum Chromodynamics (QCD), which is responsible for the interactions and dynamics of quarks and gluons, it remains a challenge to fully describe the QGP. One way of probing its nature is to study the properties of jets initiated inside the QGP medium with which they will interact at early times, a phenomenon known as Jet-Quenching. The interaction between a jet and the QGP will considerably change the jet's properties and characteristics when compared to jets initiated in the vacuum, such as those happening in proton-proton collisions, making quenched jets an ideal probe into the QGP. In this thesis, we will explore data-driven methods to explore the characteristics of quenched jets. Of particular interest, we will focus on recent developments of generative methods, such as Generative Adversarial Networks, which can harness the underlying statistical distribution of the data with a lower-dimensional statistical parameterization, called latent space. In this space, we will be exploring how we can identify the degrees of freedom responsible for the phenomenon of Jet Quenching, and quantify it. For this, we will perform a detailed study of how the latent space variables relate to global and substructure jet observables, which are better understood from a QCD perspective, helping us to connect purely data-driven quantities with theoretical efforts.
Atmospheric Gravity Waves: a key process in Mars and Venus atmospheres
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Pedro Machado

Co-Supervisor: Gabriella Gilli

Institution: FCUL (Universidade de Lisboa)

Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço

Abstract

Recent observations by Venus Express (VEx) spacecraft [Svedhem+2007,Drossart+2007] and ground-based campaigns, allowed to carry out an unprecedented characterisation of winds [Machado+2014, 2017,Peralta+2017a] and atmospheric temperatures of Venus [Limaye+2017]. Those new measurements significantly improved our comprehension of Venus atmospheric circulation and achieved new valuable constraints in atmospheric dynamics of planets with superrotation. At the same time, they put in evidence the high variability of the Venus atmosphere, and they opened new scientific questions such as: what processes control the transition region (70-120 km) between the retrograde superrotating zonal flow and day-to-night circulation? How does the interplay of planetary and small-scale waves control the circulation features? We propose a systematic characterisation and classification of the waves apparent on Venus using remote sensing images from VEx and Akatsuki (Nakamura+2007) cameras. This systematic characterisation of atmospheric waves is of critical importance to constrain current sophisticated 3D models of terrestrial planet atmospheres [Gilli+2017].
Search for new physics in exclusive processes at the Large Hadron Collider.
Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Jonathan Hollar

Institution: Instituto Superior Técnico (Universidade de Lisboa)

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Abstract

The subject of this thesis is the search for New Physics in exclusive processes at the Large Hadron Collider (LHC). Production of exclusive processes occurs with high cross section in gamma-mediated processes at the LHC. Photon-photon collisions may provide the conditions to study particle production with masses at the electroweak scale. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to select exclusive processes and probe the standard model (SM). PPS is a detector system at approximately 210 m from the interaction point around the CMS detector, and it is designed to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive processes. Since 2016, PPS has been taking data in normal high-luminosity proton-proton LHC collisions. The goal of this research project is to select and identify for the first time in data the extremely rare processes of heavy particles – including lepton pairs, top quarks and W bosons - produced exclusively and identified together with proton tagging. The research will be carried out in the context of the Portuguese participation in the CMS experiment at the LHC in the more general context of the searches for New Physics processes at the LHC, in the framework of the activities of one of the outstanding research groups in High-Energy Physics in Portugal. Citing the Report of the recent Institutional Evaluation performed by an international review panel nominated by FCT: “The LIP-CMS group, while small in size, is really outstanding and world-class”. The candidate is expected to work in a team with a group of researchers.