Call

Brighter and Radiation-harder Scintillators for Future Calorimeters

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Rute Pedro

Co-Supervisor: Patricia Conde Muino

Co-Supervisor: Henric George Sacha Wilkens

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

Radiation hardness is a crucial challenge of future detectors either operating at the high luminosity LHC phase or installed at the next frontier CERN colliders. Calorimeters are indispensable instruments to measure the energy of the collision products and designs based on organic scintillators and wavelength-shifting (WLS) fibres read by photodetectors are common due to low cost and good performance. This research exploits the current operation of the ATLAS Tile hadronic calorimeter to model the radiation damage of scintillators and WLS fibres in the real experimental environment. Several factors contribute to the total light output of scintillator+WLS fibre calorimeters, such as fibre length, scintillator plate/tile sizes, dose, dose rate and others. The plan will explore how these factors correlate with the light yield degradation using regression techniques based on modern machine learning and will involve international collaboration within the ATLAS Tile calorimeter group. In parallel, R&D on new materials for brighter and radiation-harder scintillators for the harsher radiation conditions of future experiments will be carried on at laboratory in collaboration with the Institute for Polymers and Composites of the University of Minho. The scintillator samples will be characterised in terms of light yield, attenuation length and resistance to ionising radiation at the LIP Laboratory of Optics and Scintillating Materials.

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

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

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.

Testing the Cosmological Principle with Structure Formation probes and Artificial Intelligence

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio da Silva

Co-Supervisor: José Pedro Mimoso

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

The cosmological principle is at the heart of modern cosmology. Combined with the Einstein field equations it leads to the homogeneous and isotropic Lambda Cold Dark Matter Friedmann-Lemaitre-Robertson-Walker (FLRW) models that have become the present baseline paradigm to analyze and predict large-scale cosmological datasets. Yet the Universe closer to us exhibits remarkable inhomogeneities such as voids, filaments, and a plethora of structures which suggest that a more general class of non-homogeneous Lemaitre-Tolman-Bondi (LTB) models should be considered to accurately describe observations. The forthcoming ESA/Euclid satellite mission will scrutinize the homogeneity baseline paradigm over a wide range of cosmological scales with a variety of probes. The Euclid mission will observe billions of galaxies in the visible and infrared sky for weak gravitational lensing and galaxy clustering studies. The data will be used to investigate the nature of dark energy, dark matter and gravity as well as to test the validity of the cosmological principle on a range of distance scales using survey tomographic information. This project addresses the problem of structure formation in the context of non-homogeneous models. It proposes the study of the observational signatures of these models and new ways of confronting them with future Euclid data. The project includes the development of estimators and unsupervised machine learning heuristics to probe the validity of the cosmological principle at different scales as well as the development of a set of numerical tools to generate mock simulations of cosmological volumes and projected mass maps that can be used to simulate Euclid observations. The proposed approach should allow to obtain FLRW asymptotic behavior on very large scales and to model the transition scale between homogeneity and non-homogeneity for different LTB model hypothesis.

Quarks and gluons in a hot medium: propagators, confinement and chiral symmetry restoration

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Paulo Silva

Co-Supervisor: Orlando Oliveira

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

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

Quantum Chromodynamics (QCD) describes the interactions between quarks and gluons. One of the puzzling properties of QCD being that its fundamental particles, i.e. quarks and gluons, are not observed in nature but appear as constituents of mesons and baryons. In strong interactions two of its main open questions are the understanding of confinement (why there aren’t free quarks and gluons in nature) and the mechanism for the generation of mass that prevents infrared divergences. Current believe are that confinement and chiral symmetry breaking are interlaced. Further, there are indications that for sufficiently high temperatures quarks and gluons behave essentially as a gas of free non-interacting particles, i.e. they seem to be deconfined particles. The formulation of QCD on a space-time lattice enables first principles determination of the quark and gluon propagators. From the propagators one accesses information about confinement/deconfinement and on the generation of mass. The knowledge of the mass functions are crucial for the understanding of modern heavy ion experimental programs and also for the history of the Universe. In this project we aim to improve, using lattice QCD simulations, our previous studies of the QCD propagators at finite temperature [1,2,3] and, in particular, understand how the inclusion of dynamical fermions modifies these correlation functions. The main goal is to help understanding chiral symmetry breaking and the confinement/deconfinement properties of QCD as a function of the temperature by studying the properties of the various form factors that define the propagators and their analytical structure. Also the knowledge of the spectral representation allows to investigate transport properties that are of paramount importance for the dynamical description of the heavy ion experimental programs. The simulations will be performed using the supercomputer facilities at the University of Coimbra. The candidate will join a team with a large experience in lattice QCD simulations. [1] P.J. Silva, O. Oliveira, P. Bicudo, N. Cardoso, Phys. Rev. D 89 (2014) 074503 [2] P. J. Silva, O. Oliveira, Phys. Rev. D 93 (2016) 114509 [3] O. Oliveira, P. J. Silva, Eur. Phys. J. C 79 (2019) 793

Search for New Physics Phenomena with Anomaly Detection in the ATLAS/LHC Experiment at CERN

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Rute Pedro

Co-Supervisor: Nuno Castro

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade do Minho

PhD Program:

Typology: National

The Standard Model (SM) of Particle Physics is notably descriptive and predicted new particles well in advance, from which the Higgs boson discovered at CERN's Large Hadron Collider (LHC) is a remarkable recent case. However, there is paramount evidence for the need of beyond-Standard Model (BSM) physics, namely to provide dark matter candidates, explain the matter/anti-matter asymmetry, address the hierarchy problem and others. The LHC has a rich program on searches for New Physics (NP) but clues from new particles or interactions have not yet been located. Typical searches are guided by specific BSM candidates and benefit from complementary model-independent strategy, augmenting the scope of searches for signs of NP not framed by theory. This proposal is to perform a novel generic search for NP within the ATLAS/LHC experiment using anomaly detection (AD) techniques based on modern Deep Learning (DL). The DL model will learn SM physics from simulated data and then look for anomalous non-SM like events in the real collision data. Detector effect anomalies can mislead the NP detection and a detailed study of this background will be considered to construct a high fidelity AD. Moreover, the impact of sources of theoretical and experimental uncertainties on the AD performance will be assessed. Benchmark NP signals will be used as tests throughout the AD development. The project will be integrated in the ATLAS Portuguese group, and collaboration with several international groups is foreseen. Synergies with the LIP Competence Centre for Simulation and Big Data and with the LIP Phenomenology group will be explored, namely to investigate approaches for experimental result interpretability and recasting into theory exclusion limits.

Search for the two-neutrino and neutrinoless double beta decay of 134Xe with the LZ detector

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Elias Lopez Asamar

Co-Supervisor: Alexandre Lindote

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

The fact that neutrinos have mass is one of the most important evidences of physics beyond the Standard Model. A relevant hypothesis that could explain this fact is the Majorana mechanism, that assumes that neutrinos and antineutrinos are the same particles. If this hypothesis were true, then certain nuclei could decay by emitting only two electrons. For this reason, several experiments are aiming to confirm the Majorana hypothesis by searching for this very rare process, called neutrinoless double beta decay. While the observation of neutrinoless double beta decay in a given isotope would be a sign of new physics, it would be necessary additional checks to confirm the Majorana mechanism. In this context, observing the neutrinoless double beta decay in both 136Xe and 134Xe isotopes would provide a strong support in favour of the Majorana mechanism. While the neutrinoless double beta decay of 136Xe is being intensively studied, more research is needed for that of 134Xe. Therefore, this thesis is proposing to be involved in the search for the neutrinoless double beta decay of 134Xe with the LZ detector. Although the primary goal of this experiment is the search for dark matter, it is expected to lead the sensitivity to this process in the next few years. This experiment will start operations in early 2021, and therefore the student will be able to contribute to the analysis of real data. This work is expected to lead to a high-impact publication. As a side study, the student will also develop the search for the two-neutrino double beta decay of 134Xe, that is among the rarest known processes in the universe.

An innovative detection concept for neutron imaging and neutron scattering applications in life sciences and material research

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Luís Margato

Co-Supervisor: Andrey Morozov

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

Neutron Detectors, integrated in sophisticated instruments at large scale neutron facilities, such as ILL- Institut Laue-Langevin (FR), ISIS - Neutron and Muon Source (UK), FRM II - Research Neutron Source Heinz Maier-Leibnitz (DE) and the ESS - European Spallation Source (SE), are crucial tools for revealing the structure and function of matter from the microscopic down to the atomic scale, using neutrons as a probe. Recent examples of progress achieved in answering big challenges include advances in Alzheimer's disease research, study of viruses such as HIV-1, and development of new materials for hydrogen storage, lithium-ion batteries and solar cells. Being neutrons a powerful probe in structural biology, neutron-based methods are also expected to help to unveil crucial features of SARSCoV-2 virus, needed to design effective drugs. The importance of neutron-based methods for society is recognized by the EU which has invested 2 billion euros in the ongoing construction of the next generation neutron facility, the European Spallation Source (ESS), which is one of the world’s largest scientific and technological infrastructures being built today. However, in order to achieve the full potential of this investment, the scientific community has to develop new neutron detectors with performance beyond the current state-of-the-art. This thesis project is focused on the development of an innovative 10B-RPC based detection technology for neutron diffraction, reflectometry and Time-Of-Flight neutron imaging applications. The concept is based on the Resistive Plate Chambers (RPC), a technology widely used in large-area detectors in high energy and astroparticle physics, combined with solid-state neutron converters enriched in 10B isotope, needed to provide sensitivity to thermal neutrons. One of the main goals of the project is to make the next step in the development of this novel concept by reaching high counting rate capability (>100 kHz/cm²), combined with a high spatial resolution of about 0.1 mm, a neutron detection efficiency above 50%, a gamma sensitivity below 1E-6, and a nanosecond time resolution. The PhD project involves the following steps: investigate new detector architectures; develop mathematical models of the detector response; develop new position reconstruction algorithms based on statistical methods and machine learning techniques; perform comprehensive simulation-based design optimization; develop and construct the detector prototypes; experimentally test and characterize the prototypes on a neutron beam-line. The project is to be conducted in the Neutron Detectors Group of LIP. The group has deep experience in development of novel particle detection techniques in general and for neutron imaging in particular. It is also well recognised internationally and has strong involvement in several large-scale international collaborations. This PhD project provides a unique opportunity for the candidate to be fully embedded in a strong international collaboration with the detector groups from the world-leading neutron facilities in Europe (ISIS, ILL and FRMII), opening a path to the next stages of the scientific career. Experimental campaigns to test the detector prototypes at the large-scale neutron facilities are also foreseen during this PhD project. For more information, please contact Dr. Luís Margato (margato@coimbra.lip.pt) or Dr. Andrey Morozov (andrei@coimbra.lip.pt).

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

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

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. One initial direction will be 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. Another is the use of symbolic regression to seek model-independent information direct from data (see e.g. arXiv:1905.11481). The project may contribute both to the group’s activities in Euclid satellite preparation, validation and ultimately data analysis, and to Andrew Liddle’s work in the ongoing Dark Energy Survey.

Development of data analysis methods for the observation of the Migdal effect

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Elias Lopez Asamar

Co-Supervisor: Francisco Neves

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

The existence of dark matter in the universe is considered one of the most clear indications of the possible existence of new physics not described by the Standard model. In this context, direct detection experiments aiming to search for dark matter particles that reach the Earth are of utmost importance. To date, direct detection experiments have typically searched for dark matter particles with mass above few GeV, but no conclusive signal has been observed yet. This fact has led to a very active area of research dedicated to develop new approaches to search for dark matter particles beyond the current experimental limits. One of such new approaches is based on the so-called Migdal effect, namely the predicted emission of an atomic electron when the respective atomic nucleus is perturbed. The exploitation of this phenomenon is considered as one of the most promising directions to search for dark matter particles with mass down to few hundreds of MeV. However the Migdal effect has not been observed yet. For this reason, a team of collaborating institutes that include Rutherford-Appleton Laboratory (UK), LIP-Coimbra and CERN (Switzerland) is developing an experiment to confirm the existence of such process. In this experiment, the Migdal effect will be induced in atoms of a gaseous target using fast neutrons. The purpose of this thesis is to contribute to the data analysis of such experiment. For this reason, the candidate will become a member of the respective collaboration. She or he will develop methods that will be applied to the collected data in order to search for events where the Migdal effect occurs. This work will include the exploration of machine learning techniques to identify the neutron-nucleus interactions where the Migdal effect occurs. This will involve to reconstruct the energy and the position of the particle tracks resulting from the neutron-nucleus interactions, and to develop discriminating algorithms that will allow us to identify the occurrence of the Migdal effect.

Searching for new physics with Higgs and vector bosons at the highest energies with the ATLAS detector

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Inês Ochoa

Co-Supervisor: Patricia Conde Muino

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

The Standard Model of Particle Physics (SM) is a very successful and precise description of particle interactions, yet it leaves unexplained several observable phenomena, such as gravity or dark matter. Therefore, after the discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider (LHC), searching for new physics beyond the SM (BSM) is the main focus of the LHC experiments. Various extensions of the SM have been proposed to address the open questions in the field, from extra dimensions to supersymmetry, which typically predict the existence of new heavy particles in the TeV scale, that can be within reach of the LHC. Given their central role in electroweak symmetry breaking, the W, Z and Higgs bosons are potential windows into BSM physics and can lead to the discovery of new particles. This project foresees the exploration of final states with two high-energy (boosted) bosons in the search for new heavy particles or for indirect signs of their presence. ATLAS detector data with boosted W, Z and Higgs bosons, as well as novel non-SM bosons, will be analysed using their fully-hadronic decay channels. The candidate will explore the Run 2 dataset for signs of new physics by taking advantage of state-of-the-art techniques that can identify boosted bosons and distinguish them from background processes with cross-sections that are several orders of magnitude larger. Entirely unsupervised searches via anomaly detection methods will also be examined, with the aim of ensuring a thorough and model-independent exploration of the dataset. The candidate will work with a team at LIP which has expertise in the development of the boosted techniques used in ATLAS and that has played leading roles in the latest ATLAS publications in these final states. The candidate is also expected to develop their research along with members of other institutions that are part of the ATLAS Collaboration, contributing to the successful operation of the experiment and to travel to CERN to present their work.

Probing the primordial quark gluon plasma

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Yen-Jie Lee

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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 exceptional capabilities of the CMS detector (in particular the muon and tracking systems) make it possible to identify and fully reconstruct b-quark states for the first time ever in ion collisions. 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 and the rarer Bc meson). 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. The Thesis project involves the analysis of datasets collected by the CMS experiment in heavy-ion and proton-proton collisions at the LHC. The project is developed within the CMS working group formed by researchers from LIP and MIT.

Is the neutrino its own antiparticle? - 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

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

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 experiments. LUX-ZEPLIN (LZ) is one of such detectors, employing ten tonnes of liquid xenon with a total of 630 kg of Xe-136 in its sensitive region. A preliminary study using simulated data showed that it can reach a sensitivity of 1.06×10^26 years after 1000 days, 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 once the detector starts acquiring data in early 2021. A next generation detector is already being planned, with a total mass up to 10x larger, which can lead to a sensitivity 100x higher than LZ, leading to the confirmation (in case of an observation) or exclusion of the inverted hierarchy for the neutrino masses. The PhD candidate will analyse LZ data to search for this process, verifying and improving the assumptions used as much as possible, and will also conduct sensitivity studies for the next detector generation. This project also envisages the use of Machine Learning techniques, in particular classification algorithms and convolutional neural networks to explore the particular event topology of this decay, improving the efficiency to distinguish such decays from the background with the potential to reach a world leading result.

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

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: University of Manchester

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 to study the background expansion and the evolution of cosmological structure in the coupled tachyonic 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 first at the linear level against the most recent observational data. Afterwards, we shall explore the mildly non-linear regime by studying structure formation in the spherical collapse approach. Those preliminary results will then inform the study of the full non-linear regime, testing the models with non-linear data both from current and future developments.

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: Nuno Roma

Co-Supervisor: Frank Winklmeier

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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 2025-26, 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, 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 in computer architecture, using concurrency and multithreading and/or hardware accelerators, such as GPUs or FPGAs for handling suitable algorithmic code. The availability of High Performance Computers for offline reconstruction also makes it desirable to have software that can maximally profit from them. The study of hardware accelerators, therefore, is not only interesting for the Trigger system but also for the offline ATLAS reconstruction software. The first ATLAS Trigger GPU prototype was implemented and evaluated in 2015-16 [1]. The LIP Portuguese team was responsible for the calorimeter reconstruction algorithms. The results obtained showed the potential gain but also the limitations of the architecture and implementation done. The objective of this PhD thesis project is to contribute to the design, implement and optimisation of trigger and offfline reconstruction algorithms using GPUs as hardware accelerators, that overcome the limitations identified in the first ATLAS Trigger GPU prototype. The development will be done within the new concurrent ATLAS reconstruction framework AthenaMT, using CUDA and C++ programming languages, in collaboration with the group of High-Performance Computing Architectures and Systems at INESC-ID. In addition, close collaboration with researches from CERN and other European institutions involved in this effort is expected. The student is expected to have availability to travel to CERN and present frequently his/her work at ATLAS Collaboration meetings. References: [1] P. Conde Muíño on behalf of the ATLAS Collaboration, “Multi-threaded algorithms for GPGPU in the ATLAS High Level Trigger”, J. Phys.: Conf. Ser. 898 (2017) 032003.

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

Co-Supervisor: Roman Pasechnik

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

Degree Institution: Universidade de Aveiro

PhD Program:

Typology: Mixed

Abroad-Institution: Lund University, Theoretical High Energy Physics (THEP) group

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.

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

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

Degree Institution: Universidade de Aveiro

PhD Program:

Typology: National

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.

Flavor Anomalies and New Physics

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Alessio Boletti

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The LHC physics program so far has been extremely successful. It has established the standard model (SM) of particle physics as a superb theory. The SM cannot however be the ultimate theory of Nature, and a major goal of the LHC for the coming years is to detect the new physics (NP) that lies beyond the SM. The most significant and exciting indications of NP, in all of the current collider data, lie in what is referred to as the “flavour anomalies”. These have persistently emerged from the data of various experiments, with their significance enhanced considerably recently at the LHC. Several experimental measurements of b-quark decays present discrepancies with the SM prediction. As of today, the angular analysis of the flavour-changing neutral currents (FCNC) decays show the most significant anomaly. Such processes are highly sensitive to the presence of NP particles, like new gauge bosons (Z'), LeptoQuarks (LQ), and scenarios with extended scalar sectors (2HDM). The CMS detector has accumulated, from 2016 to 2018, a very large data sample dedicated to the angular analysis of several FCNC decays with a pair of muons in the final state. The analysis of this sample allows for measurements with world-leading precision. In this Thesis project the student will take part in the analysis of this dataset, with the angular analysis of FCNC decays, and help in the preparation of the data collection during the upcoming LHC run, developing machine-learning algorithms to identify these rare decays in the harsh environment of the LHC collisions. The results that will be obtained will contribute to a clarification of the anomalies, which is a current main priority in the field of particle physics.

Lepton Flavour Universality

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Alessio Boletti

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The most significant indications of NP, in all of the current collider data, lie in what is referred to as the “flavour anomalies”. These have persistently emerged from the data of various experiments, with their significance enhanced considerably recently at the LHC. The anomalies imply a departure from Lepton Flavour Universality (LFU), a backbone of the SM, thus having far reaching consequences. They are detected through measurements of b-quark decays to leptons. Such processes are highly sensitive to the presence of NP particles, like LeptoQuarks (LQ) and new gauge bosons (Z'). The CMS detector has accumulated one of the largest heavy flavour datasets ever recorded. A dedicated data sample designed to facilitate the investigation of the LFU anomalies has been collected during LHC Run2 by CMS. In this Thesis project the student will take part in the analysis of this dataset, with measurements of LFU in B meson decays, and develop new techniques based on machine-learning algorithms for the reconstruction of these decays in the preparation of data collection during the upcoming LHC run. The results that will be obtained will contribute to probing a fundamental principle of the SM and to a clarification of associated anomalies.

Cosmic-ray isotopic composition with the AMS detector and its implications on cosmic-ray propagation

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Fernando Barao

Co-Supervisor: Laurent Derome

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: Laboratory of Subatomic Physics & Cosmology (IN2P3/CNRS)

AMS (Alpha Magnetic Spectrometer) is a unique particle physics experiment that was installed on May 2011 in the International Space Station Facility (ISS), orbiting around earth at an altitude of 400 km. After nine years of continuously data taking an unprecedented large number of all cosmic ray charged species have been gathered with rigidities ranging from hundreds of MegaVolt (MV) to few TeraVolt (TV). The inclusion in the AMS spectrometer of a Ring Imaging Cerenkov Detector (RICH), provide both an independent measurement of the particle velocity with a precision of at least 0.1% and of the electric charge. Such a good resolution allows to perform isotopic separation on a large kinetic range and for different nuclei charges when compared to previous experiments. The importance of measuring light isotopic particle in cosmic rays like ^2H (deuterons), ^3He (helium), ^6Li and ^7Li (lithium) and ^9Be, ^10Be (berylium) comes from the fact that they are produced by spallation reactions of primary cosmic rays accelerated from supernova remnants, with Interstellar Medium (ISM). Its abundance upon arrival to earth when compared to their progenitors abundance provides important constraints to the cosmic ray propagation models. The integrated analysis of the different isotopes in AMS require the study of specific selection criteria including machine learning techniques in order to reject eventual background that can be very dominant in some species. Data selected has to be corrected by the experiment time of exposure together with efficiencies related to the detector. Strategies to balance a good data selection while keeping backgrounds under control, have to be developed, aiming at explorating species energy ranges as wide as possible. In addition, AMS experiment is also unique since its data has been impacted since its launch on 2011 by solar activity for about a full cycle (around 11 years). The study of the time variability of these spectra is also of outstanding importance to better understand solar influence on cosmic ray fluxes of different species and different velocities. The student will develop his activities in the framework of the AMS collaboration that meets several times per year at CERN and will be integrated in the AMS/LIP (Lisbon) and AMS/LPSC (Grenoble, France) groups.

Searching for the rarest decays in the Universe

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Alexandre Lindote

Co-Supervisor: Claudio Frederico Pascoal da Silva

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

The rarest nuclear process ever observed in laboratory is the double electron capture (2𝜈2EC) in Xe-124, with a half-life of 1.8x10^22 years (10^12 times longer than the age of the Universe!). In this process, allowed in the Standard Model, the nucleus captures two orbital electrons and emits two neutrinos (124Xe+2e− → 124Te+2𝜈e). LUX-ZEPLIN (LZ) is a detector based in liquid xenon that will start operating in early 2021, and with a total of 10 tonnes of xenon can claim a >5σ discovery for this decay after just a few months of operation. Moreover, with the energy available from its high Q-value, this isotope can have two additional and even more rare decays: the emission of two positrons (2𝜈2β+) and a mixed mode with the emission of a positron and the capture of an orbital electron (2𝜈ECβ+). Although the former is too rare to be detected by the current generation of detectors, the latter is expected to have a half-life of the order of 10^23 years leading to a few hundreds of events observed in LZ, which can claim the title of rarest process ever observed. Observation of all these decay modes will contribute valuable information to improve our current understanding of nuclear models. Decay modes without the emission of neutrinos can also occur if the neutrino is a Majorana particle (i.e., its own antiparticle), providing an interesting alternative access to physics beyond the Standard Model and the nature of the neutrino other than neutrinoless double beta decay (0𝜈2β). Although their half-lives are expected to be several orders of magnitude higher than that of 0𝜈2β, resonances can occur in which the close degeneracy of the initial and final (excited) nuclear states enhance the decay rates by as much as 10^6. In particular the double capture from the L-shell in Xe-124 can have a half-life as low as 10^24 years, leading to ~30 of events in LZ in 1000 days. In this project the PhD candidate will explore LZ data for these various rare decays, developing the required analysis tools and estimating the dominant backgrounds for each. A next generation detector is already being planned, with a total mass up to 10x larger than LZ, and the student will also conduct sensitivity studies for this detector which is expected to observe all the neutrino modes and set world leading limits for the neutrinoless modes with direct impact in the neutrino nature and mass hierarchy. This project also envisages the use of Machine Learning techniques such as clustering algorithms and convolutional neural networks to explore the particular event topologies of these decays, providing some additional efficiency to separate them from the backgrounds. The observation of any of these decays will undoubtedly lead to a highly impacting publication.

UHECR Physics with the Pierre Auger Observatory

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Lorenzo Cazon

Co-Supervisor: Ruben Conceição

Co-Supervisor: Pedro Assis

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: National

The Pierre Auger Observatory (formed by ~500 Physicists from ~90 Institutions) was built to study ultra-high-energy cosmic rays (UHECR), their origin and nature, as well as to study particle interactions at ultra-high energies. The main goal of this proposal is the participation in Auger, focusing on data analysis, shower and hadronic physics, where the group has recognized expertise, and to study the implications of our findings in the interpretation of the UHECR big picture. The Auger Observatory has completely reshaped the UHECR field, having established a flux suppression of the cosmic ray flux at energies above 55 EeV unambiguously and discovered that the highest energy cosmic rays have an extragalactic origin. These results support scenarios where particle acceleration takes place in sites distributed similar to the matter distribution in the Universe, with the energy losses due to the interaction with the Cosmic Microwave Background (CMB) leading to the flux suppression (called GZK cutoff) and arrival direction anisotropy. However, data on composition sensitive observables - using hadronic interaction models tuned with recent LHC measurements - require a radically different interpretation. It seems that the upper end of the cosmic ray energy spectrum is dominated by heavy particles from nearby sources for which the upper limit of acceleration almost coincides with the GZK energy. There are strong indications that hadronic interactions involved in Extensive Air Shower (EAS) are different from our expectations. Measurements show an excess of muons in EAS. that cannot be reproduced with current interaction models. The muon production depth has also been shown to have a significant discrepancy to the expectations. Understanding the origin of this inconsistencies is of great importance to break the degeneracy between primary composition and hadronic interactions models and thus solve the puzzle of UHECR. The primary scientific questions to be addressed are: a) the differentiation between the maximum energy of nearby astrophysical sources scenario and the GZK-cutoff, b) the determination of the mass composition, which is critical to understand the flux suppression, the nature of the sources and acceleration mechanisms, and c) understanding EAS and hadronic interactions at ultra-high energy. This project is mainly focused on understanding the shower physics and hadronic interactions within the air shower, with a two-fold goal. On the one side, this opens the opportunity to explore particle physics in phase-space and energy regions beyond the reach of human-made accelerators and act as a pathfinder for future accelerator experiments. On the other hand, the dominant uncertainty in the mass determination of UHECR is inherited from the uncertainties in the description of hadronic interactions. Reducing this uncertainty is crucial to solve the puzzle of UHECR origin, and to open the way to charge particle astronomy. The experimental study of the muonic component of the shower constitutes one of the most effective ways to infer properties of hadronic interactions: the distribution of the muon number at the ground, with particular focus on its fluctuations, the Muon Production Depth (MPD), and EAS muon energy spectrum will be analyzed. There is substantial effort to experimentally access the EAS muon component at the highest energies, with the Auger Upgrade, and also at the lowest energies with AMIGA (buried scintillators) and MARTA (LIP based project, CERN/FIS-PAR/0034/2019 in this call, using RPC’s beneath the Auger Cherenkov tanks). These new experiments pose new opportunities to understand the EAS muon distributions with higher accuracy and better control of systematic uncertainties. On the phenomenology part, our group has demonstrated that the shower-to-shower fluctuation of the number of muons is mainly sensitive to the multiparticle production properties in the first interaction. For proton primaries, the muon number distribution displays an exponential tail that depends solely on the spectral features of the highest energy neutral pions that emerge from the first UHECR interaction with air. Within this project, the possibility of such novel measurements will be explored. Accessing such quantities would allow the constraint of the multiparticle production at the highest energies, in particular, the energy flow to the EM sector.

Enhancement of the measurement capabilities for the Pierre Auger Observatory

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Pedro Assis

Co-Supervisor: Lorenzo Cazon

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: National

LIP has been leading within the Pierre Auger Observatory, the development of a dedicated muon detector to develop the measurement capabilities of the Observatory, focusing mainly on the muonic component of Air Showers. Auger was built to give a significant contribution to the understanding of ultra-high energy cosmic rays (UHECR), their origin and nature, as well as to study particle interactions at such high energies. The data taken by Auger led to several breakthroughs in UHECR physics. A suppression of the CR flux above 5.5x10^19 eV is firmly established, and the fine structure of the spectrum starts to unveil. A dipolar asymmetry on the arrival directions has been observed, strongly supporting their extra-galactic origin. The CR composition at very high energies have been inferred from shower measurements, and its interpretation indicates an unexpected transition from proton to heavier elements above 3x10^18 eV. The collaboration has also a research program to estimate the hadronic interaction properties at the highest energies. One of the most intriguing results from this research area is the apparent muon deficit in predictions. Additionally, no hadronic interaction model can explain all the measured shower observables simultaneously. The obtained results present either an unexpected astrophysical panorama or even new physics at the highest energies. However, the above claim gets significantly undermined by the poor control over the shower description, i.e. over our understanding about hadronic interactions. This puts pressure on the study of the shower muonic component. Muons stem directly from the decay of charged mesons and can travel long distances being able to reach the ground. They are thus a direct link to the hadronic interaction activity within the shower. Auger has set up an upgrade program to increase the collected information for each shower. In this context, LIP is responsible for the installation of MARTA, a small array of RPCs under the WCD to perform a direct measure of the muons present at the stations. MARTA high-quality data will enable cross-calibration between different detectors and will be able to deliver physics muon measurements at E = 10^17 eV, which corresponds to the LHC centre-of-mass energy. Such measurements would allow univocal tests to the performance of high-energy hadronic interaction models. The work will be developed integrated into a multidisciplinary team which is responsible for the detector construction, commissioning, operation, data analysis, muon reconstruction and impact on the air shower physics. The candidate is expected to develop high-level analysis to tackle the so-called muon problem.

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

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

Degree Institution: Universidade de Aveiro

PhD Program:

Typology: National

After the overwhelming success of the Large Hadron Collider (LHC) RUN-1 with the discovery of the Higgs boson, the end of the RUN-2 and the absence of new resonances expected from Beyond Standard Model theories, have raised new concerns on whether or not the so called new physics lies at energies accessible to the LHC. In this scenario the next LHC run, scheduled to start at the middle of 2021, brings up great expectations for both the Theoretical and Experimental Particle Physics communities. In this regard, an important aspect that one must have in mind is the data collection and its analysis. For instance, with the expected rate of 40 million collisions per second (40 MHz), where each collision produces 1 to 1.5 Mega Bytes (MB) of information, we will have roughly 40 Tera Bytes per second, which after the end of one year of operation translates to 5000 Peta Bytes, to put in perspective, the expected amount of data for one year generated by YouTube can reach 93 Peta Bytes. This amount of data generated by the LHC is one of the big challenges for the Particle Physics community. With this state of affairs, the need to quickly process and analyze such a huge amount of information clearly calls for artificial intelligence methods, in particular, the use of Deep Learning. Although the performance of Deep learning Algorithms has greatly improved in face of the current development of General Purpose Graphics Processing Unit (GPGPU) and Field-programmable gate array (FPGA), this performance is quickly outshined when we compare it to quantum computers algorithms. The promise of such quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on their classical counterparts. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space, task that has been recently claimed by the Google AI Quantum team. In this thesis we propose the exploration of Deep Learning Algorithms, namely Deep Variational Autoencoders and Jet-tagging algorithms, tailored to use in quantum computers. These algorithms will have as main task the rapidly classification of events related to processes not expected by the Standard Model predictions, in particular rare events in the context of flavour physics and new sets of exotic particles. Later we can build new algorithms to perform data fit and constrain as much as possible new physics scenarios. To do so we will make use of the most recent TensorFlow Quantum, which is a Python framework for hybrid quantum-classical machine learning that is primarily focused on modeling quantum data. This framework allows one to build Quantum Deep Learning algorithms and test them on a simulation of quantum computers using classical computer hardware. As a concrete example of the type of New Physics scenarios that will be studied with the described techniques, we will consider heavy boosted Higgs bosons at the LHC. These are well motivated in the context of theories where the breaking of larger symmetries beyond that of the Standard Model gauge group are concerned. A particularly attractive and rather novel framework is based on a trinification Grand Unified Theory (T-GUT) supplemented by a gauge SU(3) family symmetry. This framework is inspired by an embedding into E6xSU(3) and features an unique three Higgs doublet scalar sector at the electroweak (EW) scale. Such a Higgs sector is well defined and by no means arbitrary resulting from an unification with ordinary matter at very high energy-scale. As a byproduct of this construction, hierarchies in the light fermion spectra and quark-mixing consistent with those observed in nature are automatically emergent. In essence, a thorough study of boosted Higgs at the LHC can shed light on the details of a more fundamental description of particles and interactions. With this thesis we aim at having a new set of algorithms capable of running in the next generation of quantum computers and within this a significant speed increase on data analysis processing, a crucial key for the next LHC runs as well the so long foretold 100 TeV collider.

RPCs in Astroparticle and their associated technologies

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Pedro Assis

Co-Supervisor: Ruben Conceição

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: National

The LIP group participating in the Pierre Auger Observatory has been developing the Resistive Plate Chamber technology to be used in the context of Astroparticle Physics experiments. These are normally composed of distributed stations at remote locations and have stringent requirements on power, communications and price. Currently the RPCs developed have been working with no problems in the Pierre Auger Observatory site located in the Pampa Argentina at 1400 m of altitude. The solution developed has a good timing resolution of the order of the few ns (limited by the electronics and clock synchronization) but present a modest spatial resolution of the order of tens of cm. This resolution derives from the readout panel used composed of a matrix of pads with this size. In applications for the future detectors or for the detailed study of detectors response it is desirable to reach, at least, resolution of the order of the cm that allows to achieve angular resolutions better than the degree . The simplest way of increasing the resolution is to maintain the readout paradigm and simply reduce the pad size. However this would lead to a growth of the number of acquisition channels with the number of pads to the square. The aim of this thesis is to explore and develop solutions in which the increase on the resolution grows, at most, linearly with the factor gained in resolution. Changes can be considered at the detector level but solution will be investigated in the changing of the readout paradigm and on the instrumentation of the detector. The thesis will focus on the development of solutions having in mind the requirements posed by the novel SWGO experiment, a large-sky gamma-ray observatory to be installed in the southern hemisphere at high altitude.

Muon hodoscopes for cross-calibration of particle detectors

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Pedro Assis

Co-Supervisor: Ruben Conceição

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: National

Astroparticle Physics observatories rely, in many cases, on the indirect detection of the primary particles reaching the Earth. The ground array technique uses particle detectors to detect the secondary particles produced in the interaction of the primary with the atmosphere. The correct estimation of the particle content is of the utmost importance. Several applications require the disentanglement of the several components of the particle pool: electromagnetic and muonic. For this, it has been deployed in the Pierre Auger Observatory a set of novel detectors to extract a correct and precise measurement of the muon component. However, the response of these detectors in field conditions is sometimes poorly known. LIP has been developing work to make a direct measurement using a dedicated detector based in the Resistive Plate Chamber technology. A spin-off has been a set of hodoscope instruments which have already been used in laboratory-like conditions to study the response of the main Auger detector. The challenge is to mount an RPC hodoscope in the field to define a muon beam. Such a beam could be used to study the response, in field conditions, of all the new detectors options being currently deployed. The thesis has a strong component in the instrumentation of RPC detectors and on the data-analysis of data produced.

Astrophysical and cosmological applications of modified theories of gravity

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Francisco Lobo

Co-Supervisor: Noemi Frusciante

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

The late-time cosmic accelerated expansion is one of the most important and chal- lenging current problems in cosmology. Although the standard model of cosmology has favoured the dark energy models as fundamental candidates responsible for the cosmic expansion, the latter may be due to modifications of general relativity, which intro- duce new degrees of freedom to the gravitational sector itself. This research project will explore the viability of a plethora of modified gravity models, consistently analyzing the reproduction of all the cosmological epochs. Specifically, we will consider general- izations of the Einstein-Hilbert action by including quadratic Lagrangians, involving second order curvature invariants, such as Lagrangians involving non-linear curvature invariants, for instance, f(R) Lagrangians and modified Gauss-Bonnet f(G) theories (and modified versions of the latter), or Lagrangians which in addition to higher-order curvature terms also include couplings to the matter sector. Another class of theories under our scrutiny will be generalized scalar-tensor or vector-tensor gravity theories, where scalar or vector fields play gravitational roles that can also be perceived as cou- plings to matter in an appropriate frame. Additionally, another fundamental goal is to study the theoretical issues of the extra degrees of freedom of the theory and fi- nally astrophysical applications in all of these classes of modified gravity will also be analyzed.

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: Constança Providência

Co-Supervisor: Francesca Gulminelli

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

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: Mixed

Abroad-Institution: Normandie Univ., Caen, France

Neutron stars are born in core-collapse supernova (CCSN) events, and, along with black holes, are one of the most compact objects in the Universe. Magnetars are a class of neutron stars that have very strong magnetic fields, of the order of 10^{15} G at the surface, and a slow rotation period, between 1-12s. In the inner crust of neutron stars, i.e., cold β-equilibrium stellar matter, light and heavy (nuclei) clusters may exist. These structures could also form in warm nuclear matter with fixed proton fraction, such as CCSN matter, and neutron star mergers. Light clusters might have an effect on the average energy of both neutrinos and antineutrinos, emitted during the supernova explosion, as they may increase or decrease it, having thus consequences on the cooling of the proto-neutron star. Consequently, transport properties can also be modified by these inhomogeneities. In fact, the outer layers of a proto-neutron star have the ideal conditions for the formation of light clusters, especially tritons and deuterons, and these clusters are not always taken into account in the equation of state (EoS) for core-collapse supernova simulations. Another site where these clusters can form are heavy-ion collision experiments. These sites can have similar temperatures and densities as in CCSN matter, but the asymmetry and charge content can be quite different. Therefore, these terrestrial experiments can also be used to set constrains on warm nonhomogeneous matter. Besides terrestrial experiments, there are also astrophysical and observational constraints, like the 2 Msun pulsars PSR J0348+0432 and PSR J1614-2230, and the recently detected MSP J0740+6620. Therefore, the construction of unified EoS, constrained by all the possible data available, is the only way towards a better comprehension of these objects, which can have implications in the direct detection of gravitational waves (GW). The recent GW detection from the collision of two NS with the LIGO and Virgo interferometers, followed up by the gamma-ray burst GRB170817A and the electromagnetic transient AT2017gfo, set a new multi-messenger era for the astronomy, nuclear, gravitational and astrophysics community. NICER has recently published the first results of a NS mass and radius. ATHENA is expected to be launched in 2028, and SKA will be ready in the 2020's. FAST will give information on the NS mass. In this project, the candidate will construct an 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, and which may advance our current understanding of compact astrophysical objects. This project is a joint collaboration between CFisUC (Univ Coimbra, Portugal) and LPC- Caen (Normandie Univ, Caen, France).

Development of novel neutron detection systems for Radiological Protection and Dosimetry, in Security and Space Applications, Proton Therapy and emerging Nuclear Technology concepts, using the neutron TOF spectrometer at CERN

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Pedro Vaz

Co-Supervisor: Alberto Mengoni

Host Institution: Centro de Ciências e Tecnologias Nucleares

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

The accurate measurement and characterization of neutron radiation fields in i) Security related applications (detection and identification of illicit trafficking of Special Nuclear Materials for nuclear security, nuclear forensics, nuclear terrorism and nuclear non-proliferation related topics), ii) Space applications (measurement and characterization of cosmic neutron radiation fields and dose for commercial aviation crews and astronauts), iii) Proton Therapy (characterization of neutron radiation fields generated by nuclear interactions of 250 MeV protons and assessment of the patients and staff radiation risk associated to neutron exposure) and iv) Emerging Nuclear Technology concepts (targets in Spallation Neutron Sources, MultiMegaWatt targets in particle factories, Accelerator Driven Systems for the transmutation of high radiotoxicity nuclear waste), impose stringent requirements in the availability of accurate neutron interactions´ cross-section data. Modelling and simulation of these neutron radiation fields and of neutron detection systems via Monte Carlo, deterministic or hybrid calculations also dictate the need for neutron and proton interaction cross-section data for accurate particle transport simulation. Many of the specific requirements for accurate cross-section data concern neutrons in the energy range of several tens of MeV up to a few hundreds of MeV. Neutron induced cross-sections data in the energy range above 20 MeV are scarce in the literature, and the existing data has not infrequently sizable uncertainties that translate in lack of accuracy in dose monitoring at workplaces. On the other hand, the neutron cross section data needs for several applications including those this proposal addresses, are included in the High Priority Request List (HPRL), an international effort conducted under the auspices of the OECD/Nuclear Energy Agency and the IAEA. The neutron Time Of Flight (TOF) facility at CERN is a premier facility worldwide allowing to perform accurate cross-section measurements of neutrons with energies spanning the range from a few meV up to the GeV. It features a high instantaneous flux, excellent energy resolution, low backgrounds and state-of-the-art spectrometers and electronics in two experimental areas. The TOF spectrometers will also be used to test the developed neutron detection concepts. Other facilities at CERN can also be used for the development and testing of detector systems´ prototypes for the aforementioned applications.

Machine Learning approaches for Gravitational-Wave Astronomy: data analysis and detection.

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Antonio Onofre

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

Degree Institution: Universidade do Minho

PhD Program:

Typology: Mixed

Abroad-Institution: University of Valencia

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].   **************************************************************************************** This work plan will be carried out under the supervision of António Onofre, José A. Font (https://www.uv.es/~jofontro/) and team members, which will be registered in the University of Minho, as formal supervisors of the PhD program (Artigo 184º of the RT-03/2020, Regulamento Académico da Universidade do Minho). **************************************************************************************** I-INTRODUCTION************************************************************************ **************************************************************************************** Thanks to the LIGO-Virgo GW detections, the stage of Relativistic Astrophysics, (Astro-)Particle Physics and Cosmology has dramatically changed in the last few years. However, there are many key scientific goals for future GW observations still awaiting confirmation: the observation of BBH mergers over the entire past history of the universe, and understanding their formation and evolution; accurate measurements of the Hubble constant and of the NS equation of state; precision tests of GR; searches for dark matter in the form of primordial BHs and in the form of ultra-light bosons (axion-like particles) interacting with rotating BHs; searches for stochastic GWs, opening a window for the understanding of the electroweak phase transition in the early universe. Anticipated future discoveries include the first BH-NS system, continuous waves from spinning NS, the unmodelled waves from a galactic core-collapse supernova (CCSN) or a long gamma-ray burst, and stochastic GW backgrounds of astrophysical or cosmological origin.  The breakthrough GW discoveries of the last few years have been possible through the synergy of techniques drawn from expertise in physics, mathematics, information science and computing. A broad range of disciplines are nowadays increasingly relying on Machine Learning (ML), Deep Learning (DL), classification problems, data mining, visualization and development of new techniques and algorithms for efficiently handling the complex and massive data sets found in “Big Data”. In the specific context of GW astronomy, the rapid increase in computing power and the development of innovative techniques for noise removal, data analysis and data-conditioning is fundamental. A single GW detector typically produces data with a rate of about 10 TB per day; even considering a reduced data set one must deal with ∼ 3 TB data/day. Most of the data collected by GW interferometers is background noise which has to be analyzed in an efficient way to increase the detection confidence and to obtain information about noise sources. ML techniques [15] can greatly help these tasks by providing tools to identify and classify noise sources, or even to disentangle GW signals from instrumental "signals" (glitches). An up-to-date summary of current applications of ML techniques to enhance the science that is possible with current and future GW detectors is presented in [16]. 

Collapsed structures in scalar-tensor theories of gravity

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Javier Rubio

Co-Supervisor: Ilidio Lopes

Host Institution: CENTRA - Center for astrophysics and gravitation

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

Many modified gravity 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 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 for the formation of primordial black holes during radiation domination or the existence of neutron stars with scalar hairs on spherically symmetric and static backgrounds. This thesis will consider the role of conformal and disformal 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, the impact of fifth forces on asteroseismology or the potential emission and gravitational memory of scalar waves. Our studies are expected to be relevant for current and future cosmological surveys such as GAIA, LIGO or LISA.

5D calorimetry at the HL-LHC: control and data acquisition from small scale systems and beam tests to large scale production

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: André David

Co-Supervisor: Pedro Abreu

Host Institution: CERN Experimental Physics Department

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

You have heard about the LHC and CMS, one of the general-purpose detector systems and collaborations that discovered a Higgs boson in 2012. We are creating a next-generation calorimeter for the LHC Phase 2 upgrade with first collisions in 2027: with 1000 m² of highly-granular silicon and scintillator detectors and 6 million individual channels, the HGCAL will provide trigger primitives every 25 ns and high-resolution space, time (25 ps precision), and energy information at an average rate of 750 kHz. You will be a part of the international team of physicists and engineers developing the control and data acquisition system of this detector. In this team we have experts in hardware, firmware, and software, and you will be able to develop your skills in any or all of them. You will also be involved in A-to-Z system aspects, debugging, commissioning, and operating detector systems, growing in size and moving from prototypes to the final components. You will be involved in the exciting period when the project will end the R&D phase and move to the production phase. You will learn about complex electronics systems using multi-gigabit technologies and will have the opportunity to use radiation-tolerant 10Gbps opto-electronics and 25 Gbps electric links. You will be expected to participate in data-taking campaigns, from cosmic muon data-taking to irradiation of electronics components (no humans harmed in the process,) and to perform your own analysis of the data collected. At the end of your time at CERN, you will have made a mark from having created the processes and systems used for the full-scale production of this novel detector.

5D calorimetry at the HL-LHC: hard real-time embedded architectures for physics performance enhancements

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: André David

Co-Supervisor: Pedro Abreu

Host Institution: CERN Experimental Physics Department

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

You have heard about the LHC and CMS, one of the general-purpose detector systems and collaborations that discovered a Higgs boson in 2012. We are creating a next-generation calorimeter for the LHC Phase 2 upgrade with first collisions in 2027: with 1000 m² of highly-granular silicon and scintillator detectors and 6 million individual channels, the HGCAL will provide trigger primitives every 25 ns and high-resolution space, time (25 ps precision), and energy information at an average rate of 750 kHz. You will be part of a team of physicists and engineers who are looking into the convergence among hardware, firmware, and software, with the goal of improving the physics performance of the detector. As part of this team you will have the opportunity to touch upon questions like as machine-learned encoder-decoder architectures for real-time triggering, real-time monitoring and automated detection and low-latency reaction, or the integration of distributed computing architectures based on Zynq-like systems-on-chip. You will then focus on one of these questions and, together with the team, follow it through studies with simulated data, implementation in hardware, and commissioning in large scale systems. You will be expected to prototype multiple ideas both in simulation and on real hardware on the way to the final goal. At the end of your time at CERN, you will have made a mark by bringing an original computing concept to bear on the physics performance of this novel detector.

Rare Higgs decays and couplings to light quarks

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Eliza Melo da Costa

Co-Supervisor: Sandro Fonseca de Souza

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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). The next big, and natural, step in this endeavour is to access the H couplings to the lighter quarks. The very high level of backround (light quarks are produced abundantly at the LHC, via QCD) renders the signals of direct Higgs decays to ligh 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 involves the search for such H 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 heart of the SM, or (even more excitingly) a first particle beyond the SM. 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 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 collaboration between LIP and UERJ/Rio groups in CMS.

Associated production of heavy flavour

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Leonardo

Co-Supervisor: Sandro Fonseca de Souza

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The LHC has provided a wealth of sensitive data collected over the last decade, which has allowed to study the production and properties of standard model (SM) particles, resulting in precision measurements of the theory and to search for new particles beyond it. The data sets that are increasingly accumulated however allow for the study of rarer phenomena, a line of research that will be pursued with correspondingly increasing focus during the high luminosity phase we're entering. The associated production of SM particles, such as of quarks of different flavour, while considerably rarer than the inclusive production of the individual SM particles, facilitates a further level of understanding of SM particle production and of sensitivity to new states beyond the SM. The production mechanisms of double parton scattering and the intrinsic heavier quark content of the proton will be probed. The goal of this Thesis project is to study the associated production of beauty and charm quarks, benefiting from the very large heavy flavor data set that has been accumulated by the CMS experiment (that contains of the order of 10^10 b-hadrons, and a few times this number of c-hadrons). This shall be achieved by employing advanced data mining procedures to distinguish such rare signals from other the more ubiquitous SM backgrounds. Final states involving the exclusive decays of b (B,Y mesons) and c (D,Psi) mesons will be simultaneously reconstructed from the collisions' decay products. Extended unbinned likelihood statistical procedures will be implemented for extracting the underlying associated production cross sections, and in turn used to probe theory expectations. The mass spectra of the hadron pair will be formed and explored. 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 project is developed in collaboration between LIP and the UERJ/Rio groups at CMS.

The Hunt for Vector-Like Matter at Colliders using Machine Learning

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Miguel Crispim Romão

Co-Supervisor: Stephen King

Co-Supervisor: Nuno Castro

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade do Minho

PhD Program:

Typology: National

Whilst one of the greatest accomplishments of modern science, the Standard Model of Particle Physics (SM) does not provide a complete picture of the fundamental degrees of freedom of our Universe. From evidence for Dark Matter (DM) to the explanation for the Electroweak Symmetry Breaking (EWSB), there are many open questions left unanswered by the SM. To address these, many Beyond the Standard Model (BSM) theories have been put forward to help expand our current understanding of Particle Physics and are actively being searched for at current and future colliders, as well as other experiments. Although there is a multitude of BSM candidates for New Physics (NP), they often share similar predictions that can be looked for at Colliders. One such case is that of Vector-Like matter, a set of new fermions not belonging to the SM which the Left and Right components are in the same representation of the Gauge group. For example, Vector-Like Quarks often arise in Composite Higgs models as new states of the strong dynamics underlying the Higgs boson; another example is that of Vector-Like states present in Grand Unification Theories, where remnants of larger Gauge representations can produce extra matter states at low energies. As such, searches for Vector-Like matter are an active area of experimental activity, with special focus on Vector-Like quarks at the Large Hadron Collider and Vector-Like Leptons at the Future Circular Collider. In this thesis, we will systematically explore the viable BSM candidates with Vector-Like matter. For this, we will take two complementary approaches. On the one hand, we will explore how novel Machine Learning techniques can help us to understand regions of the parameter space of Vector-Like models that are being overseen by current experimental analysis assumptions and frameworks. This will help us better understand the limitations of current searches and what this means to different classes of BSM models with Vector-Like matter. On the other hand, we will use Machine Learning to systematically explore the parameter space of specific Vector-Like matter realisations to further constrain them and assess whether there are kinematic regimes that have been overlooked by experimental searches. The work for this thesis will be carried out within LIP Phenomenology group, in collaboration with the Competence Centre for Simulation and Big Data at LIP, and the student is expected to participate in international collaborations with the University of Southampton. The student will benefit from a supervision team that covers expertise on Theoretical and Experimental Particle Physics, as well as Machine Learning. This will allow the student to contribute with novel tools in Particle Phenomenology, which can be further developed with LIP ATLAS and CMS groups.

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

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: German Cancer Research Center (DKFZ)

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.

Particle production in inflationary cosmology

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: João Rosa

Co-Supervisor: Roberto Vega-Morales

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

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: Mixed

Abroad-Institution: University of Granada

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.

Bridging theory to experimental data to unveil QGP time structure

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Liliana Apolinário

Co-Supervisor: Leticia Cunqueiro

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

Heavy-Ion collisions are an essential part of the current and future physics program of high energy colliders. They allow to uniquely test our fundamental understanding of the theory of strong interactions (QCD) in extreme conditions of temperature and density (the Quark-Gluon Plasma, QGP). The Large Hadron Collider (LHC) at CERN is now preparing future upgrades to increase luminosity and centre-of-mass energy. For heavy-ions, this will unlock novel measurements to probe the rapidly evolving QGP medium and to unravel its inner workings dynamics. Among the possibilities to study its properties and evolution, hard probes, such as jets, have shown massive potential as they opened the first exploration avenue for QGP time-evolution analysis. In this thesis, the student is expected to constrain the analytical description of the medium-induced modifications that a jet experiences when travelling through the QGP - a process known as jet quenching -, and, ultimately, to measure the QGP properties and its time evolution. This work plan will be at the forefront of current efforts, comprising a robust theoretical and phenomenological approach to bridge current jet quenching models to experimental data. It includes the design of novel jet and jet substructure observables to disentangle medium-induced effects, QGP tomography exploratory analysis and development of jet quenching models and its implementation in current Monte Carlo event generators. For that, the student will be co-supervised by Liliana Apolinário (at LIP) and Leticia Cunqueiro (at CERN, member of the ALICE collaboration), benefiting from close collaboration with both theory and experimental communities of Portugal and CERN.

Disentangling and Quantifying Jet-Quenching With Generative Deep Learning

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: José Guilherme Milhano

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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.

Development of High-Precision Timing Detector for the CMS experiment at HL-LHC

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Joao Varela

Co-Supervisor: Tahereh Niknejad

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The subject of this thesis is the development of a new high precision timing detector for the CMS experiment in the High-Luminosity phase of the LHC accelerator (HL-LHC) starting in 2027. The HL-HLC would allow the CMS experiment to collect 20 times more data than available presently. These data will provide precision measurements of the Standard Model (SM), in particular the precise measurement of the properties of the Higgs boson. The HL-LHC would allow to obtain evidence of the Higgs self-interaction, allowing the measurement of Higgs field potential for the first time. This measurement is crucial for a deeper understanding of the Higgs field, which may give possible hints for physics beyond the SM. The HL-LHC requires challenging new particle detectors in order for the experiment to handle the huge protons collision rate. At the LHC, proton beams are organised in bunches that collide every 25 nanoseconds. The bunch crossing time is of the order of 1 nanosecond. In the HL-LHC an average of 200 proton-proton collisions will occur at each bunch crossing, creating a challenging background to the rare events in particular those where Higgs bosons are produced. In order to cope with this challenge, the precise measurement of the time of production of the charged particles is required. The timing information provides a powerful discrimination of background, allowing to correlate particles from the same interaction and to identify clean events. The current detectors can achieve a time resolution of the order of 0.5-1.0 nanoseconds, which is insufficient to maintain the sensitivity to rare physics processes in the HL-LHC era. A strong R&D program towards a precise timing of charged particles is now underway aiming at a time resolution of the order of 30 picoseconds, representing an improvement relative to current detectors by a factor ~20. The LIP-CMS group is strongly involved and has coordination responsibilities in 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. The PhD student is expected to play a major role in this research. 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, in particular in the detection of double Higgs production and the measurement of the Higgs self-interaction parameters. 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”.

Heavy Flavour Jets Production in Heavy Ion Collisions in Run 3 of the LHC with the ATLAS Detector

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Helena Santos

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

Context: Ultrarelativistic nucleus-nucleus collisions at the Large Hadron Collider (LHC) provide an unique opportunity to recreate the Quark Gluon Plasma (QGP) in the laboratory energy frontier. This plasma of quarks and gluons, which is known to behave as a nearly perfect liquid, was the prevailing state of the Universe shortly after the Big Bang. The capabilities of ATLAS, namely large acceptance and high granularity calorimeters, afford excellent handles for QGP studies. A major goal of the Heavy Ion Program of the LHC is the understanding of the effects of the QGP on jets, namely the study of the nature of the energy loss suffered by the quarks and gluons while crossing the QGP. The bottom quark, in particular, constitutes an excellent probe. Due to its large virtuality, Q, it has a formation time,∆t ≈1/Q ≈ 0.1 fm/c, much smaller than the formation time of the QGP at the LHC (≈10 fm/c). The understanding of the nature of the energy loss (either collisional or gluon radiative), by its turn, is crucial to infer the properties of the QGP. The HI ATLAS/LIP group is contributing with important developments preceding the b-jet physics analysis, namely on b-jet reconstruction, b-tagging and b-jet triggers in HI collisions. Objectives: The student will participate in Pb+Pb data acquisition at CERN already during Run 3 (expected for the Falls of 2022-23-24) and will analyse the data. The analysis will explore strategies, namely machine learning techniques, to separate the b-quarks jets from light jets (mostly u- and d-quarks) and further separation of b-quarks jets originating directly from the hard process from those arising from gluon splitting with the aim of devising novel experimental observables sensitive to the different energy loss of quarks and gluons. Requirements: This is an experimental PhD program. The work will be developed at LIP - Laboratorio de Instrumentacao e Fisica Experimental de Particulas. The student should have solid computing skills, namely in C++ programming. Furthermore, she/he will concurrently participate in the technical activities in which the ATLAS/LIP group is involved, namely in the Tile calorimeter and/or in Trigger systems.

Heavy Flavour Jets Production in Heavy Ion Collisions at the High Luminosity LHC with the ATLAS Detector

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Helena Santos

Co-Supervisor: Patricia Conde Muino

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

Context: Ultrarelativistic nucleus-nucleus collisions at the Large Hadron Collider (LHC) provide an unique opportunity to recreate the Quark Gluon Plasma (QGP) in the laboratory energy frontier. This plasma of quarks and gluons, which is known to behave as a nearly perfect liquid, was the prevailing state of the Universe shortly after the Big Bang. The capabilities of ATLAS, namely large acceptance and high granularity calorimeters, afford excellent handles for QGP studies. The ATLAS experiment is strongly committed with the HI program of LHC and great expectations on the capabilities of the Upgrade to bring deeply understanding on the nature of the QGP are raised. A major goal of the Heavy Ion Program of the LHC is the understanding of the effects of the QGP on jets, namely the study of the nature of the energy loss suffered by the quarks and gluons while crossing the QGP. The bottom quark, in particular, constitutes an excellent probe. Due to its large virtuality, Q, it has a formation time,∆t ≈1/Q ≈ 0.1 fm/c, much smaller than the formation time of the QGP at the LHC (≈10 fm/c). The understanding of the nature of the energy loss (either collisional or gluon radiative), by its turn, is crucial to infer the properties of the QGP. The HI ATLAS/LIP group is contributing with important developments preceding the b-jet physics analysis, namely on b-jet reconstruction, b- tagging and b-jet triggers in HI collisions. Objectives: The goal of the proposed thesis is the prospective study of the Heavy Flavour jets produc- tion in the HL-LHC phase (expected to start in 2027) benefiting from the 1 order of mag- nitude increased luminosity foreseen for the Pb+Pb runs. The most important ATLAS upgraded components for the proposed project are the calorimeters front-end electronics and the new tracker detector. Currently jets are reconstructed using the transverse energy of calorimeter towers (piled cells) as input signals, after subtracting the QCD underlying event. The new readout electronics of the calorimeters will provide support for a more sophisticated detector signal processing. The remaining part of jet reconstruction regards the identification of the b-jets, i.e. b-tagging. This technique aims the highest possible efficiency for tagging b-jets, with the largest possible rejection of light jets. In ATLAS the most used techniques take advantage of the relatively long lifetime of hadrons containing bottom quarks (ctau 450 mm), as well as of the hard fragmentation and the high mass of these hadrons. These properties lead to tracks in the ITk with large impact parameters (i.e., transverse and longitudinal distances of closest approach of the track to the primary and secondary vertices), on contrary to the tracks from light jets. Such a feature allows to disentangle heavy flavour jets from light jets, but it requires excellent impact parameter resolution. This is ensured by the ITk. Machine learning techniques using the properties of both the impact parameters and the secondary vertices have proven to increase sig- nificantly the b-tagging performance in pp collisions and the development in Pb+Pb is ongoing. Analysis of data taken in Run 2 and Run 3 of LHC will provide not only results on Heavy Flavour jets in HI collisions per se, but will also contribute preciously to the validation of the prospective study in the HL-LHC. Requirements: This is an experimental PhD program. The work will be developed at LIP - Laboratorio de Instrumentacao e Fisica Experimental de Particulas. The student should have solid computing skills, namely in C++ programming. Furthermore, she/he will concurrently participate in the technical activities in which the ATLAS/LIP group is involved, namely in the Tile calorimeter and/or in Trigger systems.

2 Fast 2 Furious Universe

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Tiago Barreiro

Co-Supervisor: Nelson Nunes

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

The realization that the Universe is accelerating propels the need for a dark energy component with negative pressure. This project aims to understand the nature of dark energy and how it interacts with the other particles: dark matter, neutrinos, baryons and photons. The student will construct and investigate the theoretical aspects of a class of scalar tensor theories and will evaluate its viability by testing it against current and forthcoming observational data (ESPRESSO, Euclid, Lisa). This is both a theoretical and hands on data project.

Thermal evolution of hybrid stars

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Constança Providência

Co-Supervisor: Violetta Sagun

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

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

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 physicists, in the University of Coimbra.

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

Co-Supervisor: Tim Dietrich

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

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: Mixed

Abroad-Institution: Institut für Physik und Astronomie, University of Potsdam

Despite intensive searches for the particle nature of dark matter (DM) its true nature still remains unknown. Until now, terrestrial experiments on nuclear recoil of DM, and direct searches of the DM annihilation have not yet found a suitable DM candidate. Hence, there is large interest to use astrophysical systems for the search for DM. Compact objects, such as neutron stars (NSs) are especially attractive in this context, because they can accumulate a sizable amount of DM in their stellar interior. The presence of DM inside the NS core might have a measurable effect considering NS masses and radii. Because of the recent detections of NS-NS mergers [1,2], which reveal the internal structure of NSs through the gravitational waves emitted during their coalescence, these DM effects might become measurable in the very near future. As shown in Ref. [3], an accretion of massive DM particles can significantly reduce the maximum mass of the host NS, while light DM particles can create a very extended halo around the NS leading not to decrease, but to an increase of its visible gravitational mass. At the same time, accretion of self-annihilating DM to a NS will increase its luminosity and effective temperature. In addition, presence of the DM inside the NSs during their merger might produce a distinguishable signature in the GW signal, especially during the post-merger stage [4]. Therefore, study of DM admixed NSs, and their merger dynamics with further comparison with observational data will allow us to constrain the DM properties inside the compact stars and to place constraints on the DM sector of the Universe. The focus of the PhD project is the study of the impact of DM on properties of NSs, and their merger dynamics in binary system. The main emphasis will be given to numerical-relativity simulations of the coalescence of binary systems consisting of DM-admixed NSs and on searches for the signatures of DM in the interior of compact stars. The selected candidate will establish a bridge between astrophysics, particle physics, gravitational physics, and numerical relativity. The thesis will be supervised by Prof. Constança Providência and Dr. Violetta Sagun, theoretical physicists, in Coimbra and Prof. Tim Dietrich, an expert in NS merger simulations, in Potsdam. References: [1] Abbott, B. P. et al. (LIGO/Virgo Collaborations), Phys. Rev. Lett. 119, 161101 (2017). [2] Abbott, B. P. et al. (LIGO/Virgo Collaborations), Astrophys. J. Lett. 892, L3 (2020). [3] Ivanytskyi, O. et al. Phys. Rev. D 102, 063028 (2020). [4] Bezares, M. et al., Phys. Rev. D 100, 4, 044049 (2019).

Probing the limits of the Standard Model with forward proton tagging at ATLAS

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Patricia Conde Muino

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The non-abelian structure of the gauge theory in the SM implies the existence of triple and quartic gauge boson couplings (TGC and QGC, respectively) fully constrained by the gauge symmetry. The measurement QGC provide a window into the Electroweak symmetry breaking mechanism, given the fact that the longitudinal modes of the W and Z bosons are Goldstone bosons. Deviations from the SM predictions can appear due to interchange of new particles, integrated out in the effective interaction, in new physics theories. Models with a new heavy scalar singlet interacting with the Higgs sector can modify the quartic gauge boson couplings but not the triple ones. It is, therefore, essential to probe this missing part of the SM, measuring both the TGC and QGC. 
  The ATLAS sensitivity to anomalous couplings in the γγWW, γγγγ and γγZZ vertices can be improved two orders of magnitude by using the ATLAS Forward Proton tagging detectors (AFP) [1]. AFP effectively converts the LHC into a photon-photon collider: the two scattered protons emit two photons that annihilate to produce a pair of vector bosons (two W’s, for instance). The protons, that stay intact after the interaction, are scattered through very small angles and they are detected at the AFP stations. Since there is no underlying event, the two vector bosons are the only particles produced centrally. If they decay to leptons they can be easily triggered and identified. The invariant mass of the vector boson pair 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 presence of anomalous quartic gauge boson couplings could be observed as an increase in the number of detected vector boson pairs with large invariant masses. This project proposes the search for anomalous couplings of the type γγWW using the AFP detectors. The work plan requires participating in data taking preparations and the AFP detector performance studies, fundamental to obtain the best possible proton tagging performance and, hence, the best possible sensibility to anomalous couplings. The analysis will start with the already collected Run-2 data and will later continue with the available Run-3 data (data taking starting at the end of 2021). The work will be developed in an international environment, in collaboration with experts from other European institutions. Frequent presentations of the results achieved are expected, either in collaboration meetings at CERN or by videoconference. References [1] E. Chapon, C. Royon, and O. Kepka, Anomalous quartic WWγγ, ZZγγ, and trilinear WWγ couplings in two-photon processes at high luminosity at the LHC, Phys.Rev. D81 (2010) 074003, arXiv:0912.5161 [hep-ph]. 


Exploration of hadronic interaction properties with the MARTA Engineering array

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ruben Conceição

Co-Supervisor: Raul Sarmento

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

Nature and arrival direction of cosmic rays at the highest energies can only be inferred indirectly through the analysis of the air shower induced by their interaction with the atmosphere. The understanding of the shower development relies on our knowledge about the hadronic interactions that can occur at energies well above those reachable at accelerators on Earth. Muons, being long-lived particles, carry essential information about these hadronic interactions that rule the shower development. Therefore, their detection at the ground is a crucial tool to understand the physics of extensive air showers and particle interactions at extreme energies. However, the measurement of the highest energy extensive air-showers and in particular of the produced muons poses several challenges as it has to be performed in an outdoor environment, using detectors covering a vast area. The LIP group is leading the MARTA project, which proposes an innovative concept for the muon detection in air-shower experiments. MARTA (Muon Array of RPCs for Tagging Air showers) uses an innovative technique to measure the shower muon component directly. It uses the standard water Cherenkov detector, which is sensitive to all shower components, as an absorber to the electromagnetic shower component. Resistive Plate Chambers, placed below the water tank, with a high segmentation and time resolution, can then be used to measure muons. Several full-scale MARTA prototypes are already installed and taking data in the Pierre Auger Observatory - currently the biggest cosmic ray observatory in the world - situated in Argentina. In particular, the MARTA Engineering Array (EA), consisting of seven MARTA stations, is planned to start to be deployed in Auger during 2020. This array will measure the muons on an event-by-event basis and will collect shower events produced mainly at centre-of-mass energies compatible to those reached currently at the Large Hadron Collider, LHC. Hence, MARTA EA data analysis will provide not only strong tests to the shower hadronic physics but also its successful operation would pave the construction of future hybrid cosmic ray experiments. The selected candidate will be involved in the activities of the LIP/Auger group, in particular: Participation on the commissioning of the MARTA Engineering Array; Validation of the detector concept and performance; Development of data analysis tools to reconstruct showers; Extract information from the showers using the MARTA EA and combine it with LHC to further constrain hadronic interaction properties.

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

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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

Host Institution: CENTRA - Center for astrophysics and gravitation

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The properties of the recently discovered Higgs boson together with the absence of new physics at the LHC allows us to speculate about consistently extending the Standard Model of particle physics all the way up to the Planck scale while staying in the perturbative regime. In this context, the Standard Model Higgs non-minimally coupled to gravity could be responsible for the generation of the primordial spectrum of curvature perturbations seeding structure formation and the emergence of the electroweak scale via non-perturbative effects. Interestingly enough, the predictions of this general paradigm are sensitive to the different incarnations of gravity (metric, unimodular, Palatini, Einstein-Cartan, Weyl…), opening the door to test its fundamental nature with collider experiments and future cosmological probes such as LiteBIRD. This thesis will carry out a systematic exploration of the relation between the Higgs field and gravity in the absence of new degrees of freedom beyond the electroweak scale. In particular, we will attempt to identify a self-consistent set of asymptotically scale-invariant theories to be embedded in an eventual completion of gravity and able to describe the full evolution of the Universe while potentially solving the long-standing hierarchy problem. 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. Candidates with a strong motivation and curiosity on the relation between the electroweak and the Planck scale are strongly encouraged to apply.

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

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

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

Recent observations by Venus Express (VEx) spacecraft [Svedhem+2007,Drossart+2007] and ground-based campaigns, allowed to carry out an unprecedented characterization 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 characterization and classification of the waves apparent on Venus using remote sensing images from VEx and Akatsuki (Nakamura+2007) cameras. This systematic characterization of atmospheric waves is of critical importance to constrain current sophisticated 3D models of terrestrial planet atmospheres [Gilli+2017].

ATLAS searches for rare dark matter signatures

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Castro

Co-Supervisor: Marek Tasevsky

Co-Supervisor: Miguel Crispim Romão

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade do Minho

PhD Program:

Typology: Mixed

Abroad-Institution: Institute of Physics of the Czech Academy of Sciences

Although the existence of dark matter seems to be quite plausible, its nature is still a complete mystery and collider data can be an important probe to it. The LHC collaborations have developed a comprehensive search programme for dark matter signatures, mostly based on X+MET topologies, with X being a gauge boson, an Higgs or jets. The current proposal aims at searching for rare dark matter signatures by tagging either a top quark or scattered protons, tagged at very small polar angles. The monotop signatures can be a powerful probe of specific dark matter signals, appearing in models postulating preferential couplings of beyond the Standard Model to the top quark. Such signatures rely on the tagging of an highly boosted top quark, together with significant amounts of missing transverse energy. A proper modeling of the expected backgrounds, as well as advanced machine learning techniques will be explored to enhance the expected sensitivity of this search, allowing fully benefit from the ATLAS dataset to be collected during the 3rd operation phase of the LHC. A 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 vector bosons (two W’s, for instance). The protons, that 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 vector bosons are the only particles produced centrally. If they decay to leptons they can be easily triggered and identified. The invariant mass of the vector boson pair can be measured precisely by determining the proton energy loss with the AFP detectors, even in the case of neutrinos in the final state. 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. 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. S/he is expected to contribute to the ATLAS data taking activities and also the commissioning and performance studies of the AFP detector, fundamental for the success of this project. Frequent presentations of the results achieved are expected.

Search for nucleon decay in large liquid argon experiments

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Nuno Barros

Co-Supervisor: José Maneira

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

Proton decay, and the decay of nucleons in general, constitutes one of the most sensitive probes of high-scale physics beyond the Standard Model. The most sensitive experiments up until now are mostly based on water-cherenkov signal detection, which are primarily sensitive to decay channels involving pions. The DUNE experiment is a next-generation long-baseline neutrino experiment that will use liquid argon time projection chamber (LAr-TPC) technology to detect the physics events. By using LAr, DUNE is particularly sensitive to decay channels involving kaons, adding a new set of channels to explore. The goal of this project is to pursue the search of nucleon decay modes through the Kaon decay channels. During the first run of the ProtoDUNE prototype at CERN, a specific trigger signal was put in place to identify kaons produced from the test beam. This allowed to obtain a pure sample of kaon events in the ProtoDUNE-I dataset, that can now be used to implement advanced algorithms to identify and reconstruct not only the Kaons, but also the products of their decay. This project will initially use the ProtoDUNE-I dataset to implement algorithms that will later be applied to the dataset of the second run of ProtoDUNE and used to estimate the sensitivity of the full DUNE experiment.

Calibration control and monitoring of neutrino detectors

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Nuno Barros

Co-Supervisor: Francisco Neves

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

The DUNE experiment is a next-generation long baseline neutrino experiment with a rich physics program including long-baseline neutrino oscillations, nucleon decay and atmospheric neutrinos. The experiment will use liquid argon time projection chambers (TPCs) technology, which allows to obtain large detectors with excellent tracking and calorimetry. To guarantee a precise 3D reconstruction of the physics events, it is necessary to have a detailed understanding of the detector conditions. For this reason, the DUNE collaboration has put in place a comprehensive calibration program including study of specific physics events, such as cosmic ray muons, but also using external calibration hardware like intense UV ionisation beams and dedicated radioactive sources. This project aims to implement a custom built dedicated electronics system that will permit to control the calibration hardware, and act as an interface with the data acquisition system (DAQ), monitoring and run control. This will involve the design and implementation of the electronic hardware, firmware and associated software interface. This effort will be complemented with the implementation of efficient data selection and monitoring algorithms to minimize the dead time imposed by the calibrations and optimise the quality of the calibration data taken. At a later stage, it is foreseen to leverage the experience acquired in previous activities to participate in the calibration data taking and analysis activities of ProtoDUNE run II. The project will initially focus on the development and implementation of the system in the context of the ProtoDUNE prototype at CERN, where the calibration systems will initially be deployed in 2021, with data taking expected to start in 2022. Using the experience from the ProtoDUNE data taking, it is then expected to project optimisations for the future DUNE far detector.

Development of Resistive Plate Chambers offering simultaneous precise measurement of timing and two-dimensional position

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Alberto Blanco castro

Co-Supervisor: Custódio Loureiro

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

Resistive Plate Chambers (RPC) are fast gaseous detectors traditionally used for trigger, e.g. in ATLAS and CMS, with a position and timing precision of several mm and 1 ns respectively and for timing measurements, e.g. in HADES and ALICE, with a time precision better than 100 ps. This is a consolidated and mature technology, which is commonly used in High Energy Physics (HEP) Experiments, especially when implementation over large areas is needed and an emerging technology in Astrophysics Experiments for Cosmic Rays (CR) measurements. The possibility to improve the position precision down to 100 um while keeping simultaneously the time precision at the level of 100 ps, implemented in large areas (1-2 m²) will be a major step for this technology. It could be used in particle identification (PID), by the time of flight (TOF) technique, in HEP experiments with clear advantages. The technique relies on the accurate measurement of the flight path and time by tracking and dedicated start and stop detectors respectively. By performing the measurements with detectors capable of measure simultaneously position and time each particle would be measured several times, improving timing accuracy (although on a shorter path), there would be no need for an external initial time detector, which is sometimes problematic and the cost would be reduced, since tracking would be performed at the same time with same device. Moreover, this technology would also have direct application in TOF Positron Emission Tomography (PET), where position and timing precision are crucial, in muon tomography where position precision is one of the most important parameters or in the emerging position sensitive neutron RPC detectors technology. The simultaneous measurement of position and timing with precision of 77 ps and 40 um, respectively, was firstly demonstrated by the LIP-RPC group in a small area (60 cm²) detector. Later, simultaneous position-timing measurements were also performed by other groups, however, the detector performance did not reach the level already demonstrated. Therefore, large position sensitive timing RPC capable to provide timing and position precision better than 100 ps and 100 um has yet to be demonstrated. The limitation factor to improve the position precision is not in the detector side, which has demonstrated already a position precision better than 100 um, but in the signal readout system, i.e. the RPC readout electrode configuration, the front end electronics (FEE) and the data acquisition (DAQ) system. Traditionally, in RPCs the readout is made by connecting a channel of FEE and DAQ to each of the strips used to read the signal induced by the detector. But due to the high number of strips needed to reach a resolution of 100 um over 1-2 m², this approach is not a possibility due to the high cost. Two alternatives can be explored. First one would be to connect each of the strips to a FEE and DAQ channel integrated in an Application Specific Integrated Circuits (ASIC), for this, an ASIC compatible with the signals generated by the RPC will have to be found and a system based on it will have to be designed. The second one would use some codification system of the signals readout from the strips to drastically reduce the number of FEE and DAQ channels needed. This thesis will be devoted to the study of these two approaches, with the design and construction of prototypes of RPCs and their readout systems and subsequent testing with cosmic rays or with particle beams.

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

Co-Supervisor: Francesco Pietropaolo

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Lisboa

PhD Program:

Typology: Mixed

Abroad-Institution: CERN

The technology of liquid argon time projection chambers (TPCs) allows for massive detectors with excellent tracking and calorimetry -- all crucial capabilities to meet the requirements of the next generation long baseline neutrino experiments. In this technique, electrons 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 in 2022, with the aim of taking data from 2022 onwards. The commissioning, calibration and data analysis of ProtoDUNE2 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 ProtoDUNE Phase II installation. He/she could take responsibility of the commissioning and, possibly, on early operation for a specific device of the calibration apparatus.

Measurement of top quark rare decay t->sW at ATLAS

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Filipe Veloso

Co-Supervisor: Ricardo Gonçalo

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: National

The top quark is the heaviest elementary particle known, with a mass close to the electroweak symmetry breaking, and it can provide clues about the symmetry breaking and the Higgs mechanisms. It is thus an excellent object to test the Standard Model of Particle Physics (SM). There is an important effort to study the top quark properties, like its mass, production cross-sections, electric charge, spin, decay asymmetries, rare decays, etc... Deviations from SM predictions of the production and decay properties of the top quark provide model-independent tests for physics beyond the SM. According to the SM, the top quark decays nearly 100% of the time to a W boson and a b quark. The Cabbibo-Kobayashi-Maskawa (CKM) quark mixing matrix is related to the rates of the Flavour Changing Charged Current (FCCC) decay modes. Some of the elements, e.g. Vts, were not yet directly measured but are determined from the unitarity conditions of the matrix. A direct measurement of these elements put strict conditions on the assumptions behind the matrix properties, as the existence of only three families on the SM. This research program will be developed within the Portuguese ATLAS group. It aims to measure the decay rate of the top quark into a W boson plus a s-quark with LHC data collected by the ATLAS detector using computational tools such as machine learning techniques. This result will then be used to measure the amplitude of the CKM element Vts. In addition the student will participate in the maintenance and operation of the ATLAS detector, namely in the calibration of the TileCal hadronic calorimeter. Short periods at CERN may also be required in order to collaborate in working meetings and/or shifts.

New Maps of the Dark Side: Euclid and beyond

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Host Institution: Centro de Astrofísica da Universidade do Porto

Degree Institution: Universidade do Porto

PhD Program:

Typology: National

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 increasing 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 SKA 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 SKA and relevant ELT-HIRES instruments.

Fundamental cosmology from precision spectroscopy: from ESPRESSO to the ELT

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Host Institution: Centro de Astrofísica da Universidade do Porto

Degree Institution: Universidade do Porto

PhD Program:

Typology: National

ESPRESSO is a latest-generation spectrograph, combining the efficiency of a modern Echelle spectrograph with extreme radial velocity and spectroscopic precision, and including improved stability thanks to a vacuum vessel and wavelength calibration done with a Laser Frequency Comb. It is installed in the Combined Coudé Laboratory of the VLT and linked to the four Unit Telescopes (UT) through optical Coudé trains, allowing operations either with a single UT or with up to four UTs. A key science driver of ESPRESSO is to perform improved tests of the universality of physical laws, and in particular to confirm or rule out the recent indications of dipole-like variations of the fine-structure constant. In this thesis the student will be directly involved in the analysis and scientific exploration of the ESPRESSO fundamental physics GTO, and in the preparation of any follow-up observations. Apart from its direct impact on cosmology and fundamental physics, the ESPRESSO data is also important as a reliable precursor of analogous high-resolution spectrographs for the next generation of Extremely Large Telescopes, and in particular of ELT-HIRES (in whose Phase B the student will also be involved). A second goal of the thesis is to use the ESPRESSO data for detailed and realistic simulations to assess the cosmology and fundamental physics impact of ELT-HIRES, including tests beyond the sensitivity of ESPRESSO, such as the Sandage test. The student, who should have a genuine interest and previous experience in experimental spectroscopy and astrophysical data analysis, will be working within the general framework of the ESPRESSO and ELT-HIRES science teams.

Coding the Cosmos: Simulating Superstrings in the GPU Era

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Host Institution: Centro de Astrofísica da Universidade do Porto

Degree Institution: Universidade do Porto

PhD Program:

Typology: National

Cosmic strings arise naturally in many proposed theories of new physics beyond the standard model unifying the electroweak and strong interactions, as well as in many superstring inspired inflation models. In the latter case, fundamental superstrings produced in the very early universe may have stretched to macroscopic scales, in which case they are known as cosmic superstrings. If observed, these objects provide a unique window into the early universe and possibly string theory. Recent progress in CMB polarization and gravitational wave detection highlights how some of these scenarios could be constrained by high-resolution data. However, they also show that the current bottleneck is the lack of accurate high-resolution simulations of defect networks that can be used as templates for robust statistical analysis. This will be an even bigger problem for next-generation facilities such as CORE and LISA. While most numerical simulations so far have been performed for the simplest Abelian-Higgs (or Nambu-Goto) model, realistic cosmic strings are expected to have non-trivial internal structure, includng charges and currents. Suitable analytic models are being developed, but numerical studies of these internal structures and their evolution are still lacking. 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. It will use both CAUP computational resources (including a GPU donated by NVIDIA) and international facilites accessed through PRACE (our team has 68 million core hours on Piz Daint available for the 2020-21 academic year.) The student should have an interest and relevant previous experience in computational physics, data analysis and visualisation. Experience of parallel and/or GPU programming would also be highly beneficial.

Astrophysical and Local Tests of the Einstein Equivalence Principle

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Carlos Martins

Host Institution: Centro de Astrofísica da Universidade do Porto

Degree Institution: Universidade do Porto

PhD Program:

Typology: National

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. Although they are often confused, the two are conceptually distinct, and different experiments optimally constrain one or the other. 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.

Neutron background in neutrino detectors

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Sofia Andringa

Co-Supervisor: Valentina Lozza

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

Neutrino fundamental properties may be in the origin of the matter anti-matter asymmetry in the Universe and are being searched for in experiments with different detector technologies. Neutrons, produced by cosmic muon spallation or by alpha interaction on detector materials, are an important background for low energy neutrino analyses, such as the search for double beta decay, or the measurements of solar, geo and supernova neutrinos. The aim of this project is to quantify and reduce the main uncertainties for the prediction of neutron production rates, and to measure the corresponding cross-sections in auxiliary dedicated experiments and in two running neutrino experiments, SNO+ and ProtoDUNE.

Muon tomography with RPCs

Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society

Supervisor: Sofia Andringa

Co-Supervisor: Bernardo Tomé

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

Muography and muon tomography have received a significant boost in the last decade, and will soon leave particle physics institutes to be used in many applications. Recent developments in resistive plate chamber detectors have made them more robust and able to operate in non-laboratory environment. The project will be based in use cases with different challenges, with data taking by the same RPC-based telescope from the basement of a building and in an underground mine gallery. It will address the automation of the operation and data analyses, developing the tools for self alignment and calibration, data cleaning, image reconstruction and interpretation, aiming to deliver also an end-to-end product for external users of muography.

Calibrating neutrons for DUNE

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Sofia Andringa

Co-Supervisor: Nuno Barros

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: FCUL (Universidade de Lisboa)

PhD Program:

Typology: National

DUNE will search for CP-violation in the lepton sector by comparing neutrino and anti-neutrino oscillations over a baseline of 1300 km. Neutrons are produced in different numbers in the interactions of neutrinos and anti-neutrinos, degrading the energy resolution fundamental for the oscillation measurements. This project is focused on the identification of neutrons in the DUNE liquid argon detectors, using existing data of the ProtoDUNE detectors running at CERN. It will make use of an innovative pulsed neutron source, dedicated to the low energy calibration of DUNE, and delivering a large clean sample of neutron captures. This sample will be fundamental for the training of the reconstruction algorithms and neural network methods used to classify the detailed and complex images of each neutrino interaction delivered by the DUNE detectors.

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

Co-Supervisor: Joao Varela

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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 selecting exclusive processes. PPS is a detector system to add tracking and timing information at approximately 210 m from the interaction point around the CMS detector. It is designed to operate at high luminosity with up to 50 interactions per 25 ns bunch crossing 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 the internship 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. A strong motivation and a keen curiosity are essential requirements.

Vector Boson Scattering processes at the Large Hadron Collider

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Pedro Ferreira da Silva

Co-Supervisor: Joao Varela

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The observation of a Higgs boson by the ATLAS and CMS collaborations confirmed the standard model (SM) of elementary interactions. The presence of the Higgs boson with gauge couplings compatible with those predicted for the SM provides evidence that contributions from the exchange of this boson may be responsible for preserving unitarity at high energies. However, new phenomena may be present in the electroweak symmetry breaking (EWSB) sector, where a sensitive probe of new physics is naturally given by the study of the scattering of massive electroweak bosons (known as vector boson scattering, VBS) at high energy. Any deviation in the SM coupling of the Higgs boson to the gauge bosons breaks this delicate cancellation, thus permitting a test of the EWSB mechanism. The program proposed foresees the study of VVjj (V=W,Z) final states, produced in proton-proton collisions at the LHC via VBS. The study will be performed in the leptonic final states, including the tau lepton, in the decays of the V bosons. Thanks to the correlation between different final states and the inclusion of tau leptons, sensitivity to anomalous quartic gauge couplings can be significantly enhanced over the current results. 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.

Search for Dark Matter at the LHC

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Michele Gallinaro

Co-Supervisor: Joao Varela

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

The subject of this thesis is the search for New Physics in events with jets, with W or a Z boson produced in association with large missing transverse energy. Dark matter (DM) is one of the most compelling pieces of evidence for physics beyond the standard model (SM). In many theories, pair production of DM particles in hadron collisions proceeds through a boson mediator of either spin-0 or spin-1. DM particles can be produced in pairs association jets or with a vector boson V (where V is either a W or a Z boson) and recoil with large missing transverse energy. This results in the `MET+X’ final state. 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. The candidate is expected to work in a team with a group of researchers. A strong motivation and a keen curiosity are essential requirements. 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”.

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

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

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 called “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. Searches for new physics in this channel can be significantly improved with the additional data, and with improved analysis techniques. The candidate is expected to work in a team with a group of researchers. A strong motivation and a keen curiosity are essential requirements. 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”.

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

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Instituto Superior Técnico (Universidade de Lisboa)

PhD Program:

Typology: National

Top quarks are abundantly produced in pairs at a hadron collider, and they constitute the main background to searches for New Physics. In the framework of the Standard Model (SM), each top quark decays into a W and a b quark. A good understanding of the top quark events will allow a more sensitive reach into the realm of searches for Beyond SM (BSM) processes. Recent checks of lepton flavour universality violation sparked a renewed interest towards measurements involving tau leptons, owing to a potential disagreement with SM predictions. The work will focus on studying the properties of the top quark dilepton final state and measure the tau and heavy flavour contents of top quark events. Studies of final states, including 3rd generation leptons and quarks such as tau leptons and b-jets, produced in association with top quark pair events may provide first hints for New Physics processes and shed light on the anomalies of Lepton Flavor Universality measurements. An anomalous flavor production is directly “visible” in this study. Deviations from SM predictions will indicate evidence for New Physics. 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.

Particle Heavy Weights: Higgs and Top-Quark Associated Production at the ATLAS LHC Experiment

Domain: Particle and Astroparticle Physics and associated scientific domains

Supervisor: Ricardo Gonçalo

Co-Supervisor: Yvonne Peters

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: Mixed

Abroad-Institution: University of Manchester

After an intense search, the associated production of the Higgs boson with a top quark pair was finally observed in 2018. This production channel provides the best way to directly measure the coupling between Higgs and top, the heaviest fundamental particles in the Standard Model (SM). But it also provides a way to look beyond the SM, in particular to search for signs of a non-standard Higgs boson, leading to CP-violation in the Higgs sector. Such a component is well justified in scenarios like the two-Higgs doublet model, and finding it would constitute a major discovery. In particular, it could lead to understanding why there is a huge asymmetry between matter and antimatter in the Universe. In this leading edge research, the selected student will analyze data collected by the ATLAS experiment during the LHC Run 3, to start in 2021. He or she will have the opportunity to participate in the operation of the experiment at CERN. The student will integrate the Portuguese ATLAS team and will use recent techniques developed in our group to enhance the experimental sensitivity of the analysis. He or she will be co-supervised by a colleague from the University of Manchester, where the student will spend part of the time of the PhD, as foreseen in the grant. Besides the Manchester group, the student would work in a vibrant international team within the ATLAS collaboration.

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

Co-Supervisor: Filipe Veloso

Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas

Degree Institution: Universidade de Coimbra

PhD Program:

Typology: Mixed

Abroad-Institution: University of Birmingham

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.