Thesis Proposals

In the High-Luminosity phase of the LHC physics program, the accelerator will provide an additional integrated luminosity of 3000 fb-1. One of the main challenges that must be overcome is the very high pileup (PU) originated by the high luminosity. Each of the colliding beams at the LHC consists of many intense bunches of protons. At the HL-LHC, the average number of interactions in a single bunch crossing is 200 (named ‘pileup interactions’). Most of these interactions are not interesting in the searches for New Physics at the TeV scale. They contain low transverse momentum (pT) particles and deposit little energy in the CMS detector. A relatively small fraction of all interactions are hard collisions producing particles with high pT. Nevertheless, the presence of tracks and energy from 200 extra collisions degrades the reconstruction of the hard scatter. Pileup produces many hits in the tracking detectors, leading to mismeasured or misidentified tracks. It also adds extra energy to the calorimeter measurements, such as jet energies, associated with the hard scatter collision. Electroweak phenomena, which are of special interest, are often characterized by having isolated leptons. Energy or tracks from pileup can contribute to an activity that is not due to the collision containing the leptons or photons and cause them to appear as non-isolated. In general, pileup confuses the reconstruction and interpretation of events. The development of a new Timing Detector to be integrated in the CMS experiment aims at fighting the pileup background, substantially improving the sensitivity to New Physics. In the time domain, pileup collisions at the HL-LHC will occur with an r.m.s spread of approximately 180 ps within the bunch crossing structure of the colliding beams. Slicing the beam spot in consecutive time exposures of 30 ps allows to reduce the number of vertices per exposure to about 30. A time resolution of this order would, therefore, reduce the effective multiplicity of concurrent collisions to a level comparable to the present LHC. However, the required time resolution is one order of magnitude better than achieved in the current CMS detector. The Timing Detector (MTD) is a dedicated timing layer in front of the calorimeters capable to measure the time of charged particles with a precision of 30 ps. The subject of the PhD thesis is the development of a new timing technology based on state-of-art LYSO scintillating crystals, associated to silicon-photomultipliers and Application Specific Integrated Circuits (ASICs) developed at LIP in collaboration with Portuguese industry. The thesis work will be done in the context of a collaboration with several institutes in Europe and in the US. The LIP-CMS group is fully responsible for the design and construction of the readout system of the 330’000 sensors composing the Barrel Timing Layer, benefiting from a long experience in the development and leadership of large instrumentation projects. The development and test of prototypes is carried in the TagusLIP laboratory at Taguspark, Oeiras. Stays at CERN to perform tests and measurements with dedicated proton beams at the SPS will be required. Visits to other research facilities to perform tests of resistance to radiation of the prototypes detectors and electronics are also foreseen. 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”.

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

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. The QGP has been shown to be a liquid with extremely low viscosity, the most perfect liquid ever observed, that displays collective behaviour. Understanding how collectivity emerges, that is how the QGP comes into being, from the simple interaction rules of QCD remains a challenge. One possible path, to be explored in this thesis, is to explore the way jets lose part of their energy to the QGP they tranverse and how that lost energy is equilibrated with the QGP. These studies, of how components of out-of-equilibrium probe become part of the collective QGP, allow us to tract the emergence of collectivity. In other words, one aims to understand the QGP by understanding how it reacts to perturbations due to the traversing jets. This project is expected to have a lasting impact in maximizing the potential of LHC data. The work will be carried out in LIP-Lisboa and at Lund Univsersity (Sweden) under the supervision of Guilherme Milhano and co-supervision of Liliana Apolinário (LIP) and Korinna Zapp (Lund).

The search for Dark Matter (DM) is one of the main goals of present high energy physics and astrophysics experiments. A large number of direct and indirect detection experiments together with searches at the Large Hadron Collider (LHC) have so far provided only bounds on the DM mass and couplings. In recent years the community has invested in building a large number of different experiments to indirectly search for dark matter. These experiments cover an energy range from below the MeV to above the EeV. The searches include neutrino telescopes, searches with X-Rays, Gamma Rays, Micro and Radio Waves and Charged Cosmic Rays. They will provide a comprehensive scan of a very wide range of possible dark matter candidates. The plan of the thesis is to start from simple extensions of the Standard Model and understand what is the contribution that each experiment can give to probe the dark matter sector of the model.

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 Machine Learning. Such techniques will be used as a “control” environment for Monte-Carlo event generator software tools, such as MadGraph, Pythia and CosmoTransitions.

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 this year!). 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]. 


AMS/LIP group has developed in the past expertise on isotopic separation with AMS using the RICH detector for studies on different isotopes: 2H/1H, 3He/4He and 10Be/9Be. This thesis will be co-supervised by Dr Mercedes Paniccia (Geneva University), who has devoted long efforts and has considerable experience studying cosmic ray nuclei in AMS data. During the PhD thesis, the student will explore AMS data and develop event selections tailored to the identification of isotopes, in particular Z=1 and 5 isotopes, by employing modern data analysis techniques. The student will characterize and estimate the different instrumental effects related to AMS in order to estimate the time-resolved cosmic-ray fluxes accurately. The student will then study the temporal variations of the cosmic-ray fluxes. Further interpretation of the temporal variability under solar modulation models, can be explored during the course of the thesis.

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.

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. Once produced, the QGP expands and cools very rapidiply converting into normal hadronic matter. The very short lifetime of the QGP, of around 30 yoctoseconds, requires that all probes used to study the dynamics of the QGP have to have been produced concurrently with it. Jets, the offspring of energetic quarks and gluons produced in the collision, are the most versatile probes to use the inner workings of the QGP. For realistic comparisons with experimental data, analytical calculations are complemented by simulation codes. Parton showers, the simulation of jet development, in the presence of a QGP have been developed over the last couple of decades. At present, no available parton shower encodes the wealth of theoretical knowledge we have achieved over the last few years. In particular, both the known modifications of colour coherence effected by the QGP on the parton shower and an explicit coupling of the interaction of quarks and gluons with the velocity of QGP expansion remain to be formulated in the probalistic framework of a parton shower. This project is expected to attain the probablistic formulation of both effects and their computational implementation. This project is expected to have a lasting impact in maximizing the potential of LHC data. The work will be carried out in LIP-Lisboa and at Lund Univsersity (Sweden) under the supervision of Guilherme Milhano and co-supervision of Liliana Apolinário (LIP) and Korinna Zapp (Lund).

During the course of this thesis, the student will contribute to tests of the assembly procedure, monitoring, and testing of the cooling performance on a full-scale half-disk detector inside a clean room environment. Moreover, the student will be able to work on Low Gain Avalanche Detector (LGAD) sensor testing and front end ASIC board characterisation, and to participate in test-beam activities at the SPS facility of CERN. This work will involve assisting in the setup, calibration, data-taking and final data-analysis of test-beam activities.

Quasars, thought to be hosted by a supermassive black hole (SMBH), can produce an energy release due to matter accretion that easily outshines the whole host galaxy. This energy release leads to a featureless quasi-stellar object appearance. This class of highly luminous Active Galactic Nuclei (AGN), namely, quasars, are excellent laboratories for furnishing tight constraints on galaxies' formation and evolution. Most importantly, at all redshift values, they are observed. They are also associated with the most massive and luminous galaxies in the early Universe. Several quasars were discovered over the past few years, even at early times (redshift ~7). We propose a new spectral fitting code for fitting the ultraviolet-optical range in a self-consistent manner to be applied to quasars. This code will include a standard accretion disk model (Shakura & Sunyaev 1973) and a more realistic UV-optical model from, e.g., Kubota & Done (2018). We will tie these prescriptions together to energetically reproduce both the observed continuum plus emission-lines in quasars considering internal attenuation. This new fitting code will also be publicly available and, additionally, be applied to ~500 000 quasars from the SDSS DR15 and produced a publicly available database catalogue for the astronomical community. This study is a preparatory work for the MOONS spectrograph in which the Instituto de Astrofísica e Ciências do Espaço co-leads. This investigation will also add value and permit incorporating the modules for fitting quasars in standard population synthesis codes.

So far, gravitational waves have been described in the context of homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) models. A more general class of non-homogeneous Lemaitre-Tolman-Bondi (LTB) models may be a more natural and an observationally consistent alternative to the present homogeneous and isotropic paradigm. Predictions for gravitational waves from the early universe and from astrophysical sources are still missing for this class of models and are necessary for the preparation of the next ESA flagship missions for cosmology: LISA and Euclid. The main objective of this project is to develop the framework of GW generation in LTB, and build realistic simulations of the GW background based on it, using a combination of N-body and Machine Learning methodologies. The plan is to perform and detailed characterization of the properties of the GW signal that will be detected by future GW experiments for this class of models. We will also propose to explore the complementarity between GW and other (wavelength) surveys, using a multi-messenger approach, to identify cosmological signatures of LTB non-homogeneity in future datasets.

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

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 the last few years, 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 thesis project consists in the search for Higgs boson decays to a quarkonium state and a photon, using the large dataset collected by CMS at the LHC. The motivation for the study is to experimentally constrain the Higgs-quark couplings, and help decide whether our new boson is indeed the particle at the core of the SM, or (even more excitingly) a first particle beyond the SM.

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

Synthetic Aperture Radar (SAR) is one of the most dependable remote measuring instruments. Due to its active nature, radar operates irrespective of the weather, the presence of clouds or smoke and of light conditions (day and night), unlike optical (passive) Earth Observation programs. The growing number of satellite constellations performing SAR imaging is reducing the revisiting time towards a nearly constant coverage of the whole Earth in increasingly higher spatial resolution. Together, these factors make SAR one of the most promising data sources for monitoring Earth processes and supporting near real-time alerts for resource management and safety. However, SAR data remains a challenge to work with, even for experts. Therefore, the European Spatial Agency’s (ESA) Φ-lab, is sponsoring the development of the AI4SAR project, which has released an open-source software tool that eases the creation of datacubes of SAR data for supervised machine learning, thus making ICEYE-SAR data available to a wider user base. The thesis project explores the use of machine learning to broaden the inclusion of open SAR data sources on an open-source software package that leverages the use of SAR data by scientists beyond SAR experts. The thesis project has the potential to deliver new applications of existing or novel machine learning-based solutions for the automatic pre-processing of SAR datasets, including calibration, map projection and coregistration and others. Additionally, it may deliver a new open-source software package.

Dust is ubiquituous in the Universe affecting astronomical observations of all sources, from planets to stars to galaxies. By dimming and reddening the intrinsic luminosity, dust also affects the distance estimation of known standard candles such as Cepheids and Supernovae, which have been successfully used in the distance ladder technique to infer the cosmological origin and fate of our Universe, particularly with the discovery of the dark energy component permeating space. The proper calibration of the distance ladder, especially the adequate correction of dust effects, is a fundamental step for any meaningful cosmological analysis. In fact, it has been suggested that traditional dust assumptions are too simplistic and might play an important part in some of the current unsolved problems in cosmology, such as the Hubble tension and the mass-step for type Ia Supernovae. In this thesis, the candidate will investigate galactic dust environments, both from real survey data and simulations. For the survey data, dust maps will be built for a variety of galaxies, providing not only a novel perspective into the environments where Supernovae and Cepheids occur, but also studying dust properties for diverse locations within a large and heterogeneous sample of galaxies that have have hosted these events. By comparing the simulated galaxies with the observations, the candidate will determine the factors driving the variations in the inferred dust such as geometrical effects or dust size and composition. Correcting dust in the site of Supernovae and Cepheids will improve upon the distance ladder calibration and reduce the systematic errors in precision cosmology. Furthermore, understanding dust properties has a deep impact in many fields of astrophysics, from planetary studies to galaxy evolution, and it will help to fully exploit the power of recent missions such as JWST, which are providing data of unprecedented quality.

Axions are hypothetical particles, proposed as an extension of the Standard Model in an attempt to solve the strong CP problem in QCD. The Peccei-Quinn mechanism restores the CP symmetry by promoting the CP angle to a dynamical field - the axion - which is a pseudo-scalar field coupling to the theory. Because of their very long decay time (which is a consequence of the smallness of the CP angle), axions interact very weakly with electromagnetic fields. For that reason, axions are also very good candidates for dark matter, an issue that has attracted a great deal of attention recently. Experimental searches of axion and axion-like particles (ALPs) are based on the conversion between axions and photons. In vacuum, the amplitude of this process is extremely small, rendering detection schemes extremely ineffective. We argue that, in plasmas, the conversion probability increases by several orders of magnitude, as a consequence of the resonance in the axion-plasmon propagator. In this thesis, the candidate will investigate configurations involving plasmas as active media for the production and/or detection of axions. The investigation of some astrophysical and cosmological implications are also expected. The scientific domain of this proposal is extremely active at the international level. The candidate will most likely benefit from interactions with collaborators based on world-class institutions.

In this proposal we intend to make a relevant contribution to the questions "Where are the heaviest elements in nature produced? And can we identify an astrophysical signature of their production?" We know that light elements like hydrogen and helium are produced at the beginning of the universe, about a few minutes after the Big-Bang, and that heavier elements up to iron are produced in nuclear fusion cycles inside stars. The mechanisms of production of elements heavier than iron have also been developed for many decades. Half of the nuclei heavier than Iron can be produced in stars from the asymptotic giant branch (AGB stars) through a neutron-capture process called s-process. The "s" comes from the slow capture rate of neutrons from seed nuclei, relative to the competing reaction of β-decay. The other half, including Thorium and Uranium, cannot be produced through this process Therefore, a more extreme process is required in which the rate of neutron capture is higher than the timescale of beta-decay. This process is called rapid neutron capture (or simply r-process). However, for such a process to occur, the environment must be extremely neutron rich. For that reason, core-collapse supernovae explosions were suggested as the main site for the production of r-process elements. Yet, despite many years of research into this scenario, models and observations have failed to show clear evidence that the r-process happens in core-collapse supernovae. On the other hand, the observation of a kilonova electromagnetic transient associated with the gravitational wave signal GW170817 provided the first direct indication that r-process elements are produced in neutron-star mergers [1]. Additional events are expected to be detected in the following years, representing a complete change of paradigm in r-process research, as for the first time we will be confronted with direct observational data. To fully exploit such opportunity, it is fundamental to combine an improved description of nuclear and atomic parameters with sophisticated astrophysical simulations to provide accurate prediction of r-process nucleosynthesis yields and their electromagnetic signals to be confronted with observational data. Tables of atomic parameters (level energies, excitation/ionization cross-sections and oscillator strengths between individual levels) needed to calculate stellar opacities have large gaps, or do not exist at all, for most elements relevant for the r-process. The student will systematically calculate these atomic parameters for the different ionization stages relevant at the density and temperature range found in the ejecta expansion in a kilonova. For this she/he will use the FAC and MCDFGME codes that represent today the state of the art in atomic structure calculations. The results will serve as input for modeling the luminosity curves of kilonovas beyond the local thermal equilibrium (LTE) approximation. The PhD. research activities will be developed at LIP (Laboratório de Instrumentação e Física Experimental de Partículas), Lisbon, Portugal and at GSI (Helmholtz Centre for Heavy Ion Research), Darmstadt, Germany. The student should be available to spend a period of about two years at the GSI to apply the obtained data to the simulation of luminosity curves for different kilonova formation and evolution scenarios. [1] Kasen D. et al, Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event, Nature 551:80 (2017) https://doi.org/10.1038/nature24453

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, implying that none of the current constraints is reliable. This will be an even bigger problem for next-generation facilities such as the SKAO and LISA. Moreover, most numerical simulations so far have been performed for the simplest Abelian-Higgs (or Nambu-Goto) model, while realistic cosmic strings will have non-trivial internal structure, including charges and currents. The scientific goal of the thesis is to fill this gap, continuing the deployment of a new generation of high-scalability defect evolution codes that will match the sensitivity of ongoing and forthcoming observational searches, and using them to develop and calibrate suitable analytic models. It will use both CAUP computational resources (including a GPU donated by NVIDIA) and world-leading HPC facilites accessed through PRACE/EuroHPC. 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. The student will join a recently approved Paris-Porto-Cambridge collaboration grant.

The different remote sensing modalities, such as multispectral (MS), hyperspectral (HS), synthetic aperture radar (SAR) and light detection and ranging (LiDAR), are well established, having found real-world applications in several domains. While each imaging technology captures one of a variety of properties from the Earth’s surface, such as spectral radiance, reflectance, texture structure, height/distance, and spatial information, the complexity of most settings is better characterised by a combination of several properties. Therefore, multimodal approaches that fuse several data types achieve more detail and precision, serving a wider range of applications, and augmenting the utility of remotely sensed data. Efforts to further increase the usefulness and applicability of remote sensing data are heavily reliant on data analysis and processing. Machine learning methods, namely deep models, such as stacked autoencoders (SAEs), deep belief networks (DBNs), convolutional neural networks (CNNs), recurrent neural networks (RNNs), and generative adversarial networks (GANs) are successfully applied to each of the remote sensing modes or to a combination of them, to further augment their utility. In all deep learning cases, the robustness of image classification methods is highly dependent on the quality and quantity of samples. However, the abundance of samples is both rare and required for quality model outputs. Several methods are used to overcome the limited availability of samples. Data augmentation, such as transformation-based sample generation (TBSG) and mixture-based sample generation (MBSG), both of which synthetically enlarge the sample size. Transfer learning introduces learnt information directly to the target data, thus requiring smaller samples. Another approach to overcoming the current bottleneck of limited sample availability is the development of self-supervised or weakly supervised models. This later approach has shown promising results and is the focus of this thesis proposal. The thesis project explores the development of deep self-supervised or weakly supervised models that assume limited sample availability for the creation of multimodal composites whose data fusion significantly augments the utility of the input data. The thesis project has the potential to deliver new deep models or novel architectures which require none or less labelled data to achieve efficient image classification. Additionally, the convergence of machine learning into deep models that are general enough for reusability may justify the delivery of a new open-source software package.

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 case. However, there is paramount evidence of the need for beyond-Standard Model (BSM) physics, namely to provide dark matter candidates, explain the matter/dark-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 arisen. Events with top-quarks may directly disclose new particles from SM extensions that mix with the top quark sector, either decaying into top-quarks or produced in association with it. Specific searches are performed, for instance, in events with a boosted top-quark and missing transverse energy, in the fully hadronic topology, to probe the single production of vector-like top-quarks or dark matter signatures at the LHC. However, these searches are guided by these specific NP signals and need a complementary strategy, independent of such assumptions. This proposal is to use anomaly detection (AD) techniques, such as (variational-) auto-encoders and Deep SVDD, to search for events that are unlikely to be compatible with the SM, ensuring that if new physics is present in LHC data, it will not be missed by a priori hypothesis. Events consisting of a boosted hadronic top-quark decay and missing transverse energy collected by the ATLAS/LHC experiment will be analysed. The Deep Learning model will learn SM physics from simulated data and then look for anomalous non-SM-like events in the real collision data. The impact of sources of theoretical and experimental uncertainties on the AD performance will be assessed and benchmark NP signals will be used as tests throughout the AD development. The project will be integrated into 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.

The quark-gluon vertex being a complex function it is a fundamental correlation function of Quantum Chromodynamics that is at the heart of all Particle Physics phenomenology. At zero temperature, it is characterised by twelve form factors that explain the formation of hadrons, including confinement and chiral symmetry breaking mechanisms, and the dynamical properties of hadrons that are measured experimentally and summarised in hadronic form factors, gpd, tmd, etc. At finite the temperature the number of factor factors that are required to describe the vertex is much larger. This project aims to study, from first principles using lattice QCD simulations, how this fundamental QCD vertex evolves with temperature by computing its form factors above and below the deconfinement temperature. Implications of the temperature dependence of the vertex phenomenology will also be explored. The quark and gluon propagators will also be investigated as a function of the temperature, playing particular attention to chiral symmetry breaking/restoration by looking simultaneously to the running quark mass and the masses of scalar and pseudo-scalar mesons. Hopefully, this will help the ongoing ultra-relativistic heavy-ion collision program at LHC and at RHIC and our understanding of the dynamics of the quark-gluon plasma.

Despite its success in precisely describing particle interaction, the Standard Model of Particle Physics (SM) does not address many open questions about our Universe. Recent and future runs of the LHC of high-energy proton-proton collisions provide unique probes into the energy scales where answers may lie. A common prediction of SM extensions is the existence of new heavy particles, such as additional Higgs bosons, or W’ and Z’ bosons, which may couple preferentially to other bosons and have suppressed fermion couplings. This possibility motivates a dedicated search in the vector boson fusion production channel, for new particles that decay into W, Z and Higgs bosons. The student will develop a novel data analysis that will be uniquely sensitive to this final state signature.This search will complement the current results from the ATLAS collaboration that target new resonance searches via quark or gluon couplings. They will explore the LHC dataset at the high energy frontier and scrutinize a new corner of phase-space where new physics may be hiding. The PhD research work will be pursued in the international environment of the ATLAS collaboration, and part of it will take place at CERN. The student will be involved in the operation of the ATLAS experiment during data taking, profiting from the dataset to be collected in the 3rd experimental run of the LHC, from 2022 to 2024.

Neutrinos are very feebly interacting particles, and despite being among the most abundant in the Universe, their Nature remains elusive. By the same token, even though neutrinos are copiously produced at colliders, collider neutrinos have yet to be observed. Their detection will be a milestone, that becomes attainable with SND@LHC, the most recent experiment at CERN. The LHC delivers the highest energy man-made neutrinos, and in large amounts. These two elements (related to production cross section and luminosity, respectively) coupled to a novel, dedicated neutrino detector open up the possibility of producing and studying all three active neutrino species. The new detector has been just installed in the LHC tunnel, about 500m away from the ATLAS collision point and near the beam-line direction. We have accumulated the first data during 2022, and will accumulate much more in the coming years, during Run3 of the LHC. The thesis project offers an unique opportunity to be part of the exciting starting phase of a new experiment and small collaboration in the LHC environment.

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

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 and large areas, placed at altitudes of around 5000 meters above sea level. These experiments should be able to fight the enormous hadronic background to observe the gamma-rays. The recent observation by LHAASO of astrophysical gamma-rays with energies above PeV puts pressure to build a huge observatory with an area of at least 1 km^2 able to survey the galaxy in search of the origin of these fascinating messengers from the cosmos - the Southern Wide-field Gamma-ray Observatory (SWGO).

Primordial black holes are postulated to form in the early Universe through the gravitational collapse of large density fluctuations, via a plethora of different mechanisms. Besides accounting for a fraction or even all of the dark matter density, such black holes may have played a crucial role in the cosmic history, particularly since they are prolific particle generators, through both rotational superradiance and Hawking evaporation. In this project, the student will explore the role of these processes in producing baryons, radiation, dark matter and potentially other exotic particles in the universe, both in its early stages and close to the present day. The student will consider different mechanisms for primordial black hole formation leading to distinct mass and spin spectra, and determine the cosmological evolution of these black holes until the present day. A goal is to determine whether the above-mentioned particle production mechanisms may play a significant role in addressing the most important open problems in particle cosmology, namely the origin of dark matter, baryogenesis and reheating after inflation.

The thesis will study Beyond the Standard Model theories with extra scalar or extra vectors, and seek to constrain these theories with experimental data from the LHC and other experiments. The theories to be studied include Multi-Higgs Doublet Models, Grand Unification Theories, models with scalar or vector leptoquarks, and flavour models. These are popular classes of theories, because they are well motivated from theoretical and experimental grounds, by addressing important problems of the Standard Model.

Since its discovery, the Higgs boson became a prime tool to search for physics beyond the Standard Model (SM). At the current level of precision, the Higgs boson is compatible with SM expectations. A number of open questions indicate the existence of new physics that could be unveiled as we explore the LHC data. A wealth of experimental results from the ATLAS and CMS experiments, probe the region around the minimum of the Higgs potential, or vacuum. But the shape of this potential is not constrained experimentally. This shape is intimately connected to the breaking of the electroweak gauge symmetry, which resulted in the fundamental forces we experience today. To experimentally constrain this shape we must measure the Higgs boson self-coupling, which is accessible at the LHC through the simultaneous production of two Higgs bosons. 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. The successful student will be able to participate in the operation of the ATLAS experiment during the LHC Run 3 to start in 2022, and travel to CERN will be required.

The existence of dark matter (DM) seems to be well established by observations from different sources. However, its nature is still a complete mystery. Even if DM comes in the form of a particle its mass range is barely constrained, with values for a gauge field of the order 10-21 eV to the TeV range. As an example, the constituents of Proca stars have masses in the low range of the spectrum with the exact value depending on mass of the star. At the other end of the spectrum we have the so-called Weakly Interacting Massive Particle (WIMP) of the order of the electroweak scale. It is a simple exercise in quantum field theory to build a model that contains one or more dark matter candidates. This candidate is not constrained in its spin nor in its mass. There are many dark matter experiments of direct and indirect detection and dark matter is also searched for at the Large Hadron Collider. But different dark matter candidates can have a different impact in the observation of gravitational waves. This work is about the comparison of models with different dark mater candidates in their contribution to specific patterns in gravitational waves.

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 2022. 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. Part of the programme will take place at 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 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.

Models with larger scalar content than the Standard Model - such as the Two Higgs Doublet Model (2HDM) - can have several minima, but only one of those minima can be the "real" one. Black holes can work as catalysts between different minima, with potentially disastrous consequences. The parameters of the model must therefore be such that this vacuum transition is avoided. The constraints that one can therefore impose on the 2HDM, or other models, will therefore increase its predictive power and impact its LHC phenomenology. Can such constraints be so strong as to predict the masses and other properties of scalar particles that have yet not been discovered?

A cornerstone of the Standard Model (SM) of Particle Physics is the formulation of the electroweak interactions as arising from a spontaneously broken gauge symmetry. Experiments over the past four decades have confirmed this hypothesis with precision, most notably the LEP and SLC collider programs. The ATLAS and CMS collaborations reported in 2012 observations of a new particle produced at the CERN Large Hadron Collider (LHC) possessing properties so far consistent with those predicted for the SM Higgs boson. It should be noted, nonetheless, that the exact nature of the symmetry-breaking mechanism is not yet determined. Furthermore, regardless of the many experimental validations of the SM, it is known that it cannot be regarded as a final theory, given the many problems it fails to solve, namely the hierarchy problem, the lack of a dark matter candidate, matter-antimatter asymmetry, and others. Attempting to solve these problems, many beyond the SM theories were built. Vector-like quarks (VLQ) are featured in some of these models, as spin 1/2 fermions, color triplets with the same left and right quantum numbers, mixing with SM quarks. Both the ATLAS and CMS experiments have developed a comprehensive search program for vector-like quarks. Nonetheless, and despite a significant effort to present general results, most of these analysis made important assumptions on the production and decay modes of the vector-like quarks and thus missing possible alternative signatures, which can have strong phenomenological motivations. The current proposal foresees the development and implementation of a search for vector-like quarks which can be produced in pairs via a heavy gluon or decay into new scalars. Given the multitude of final states that vector-like quark production can have, the search strategy will rely on the use of deep learning. A complete experimental analysis, considering a detailed study of the modelling of backgrounds and sources of uncertainties will be developed. The phenomenological consequences of the experimental results will be also be studied, in close collaboration with the Phenomenology group at LIP. The current proposal will be integrated in the Portuguese ATLAS team and collaboration with several international groups is foreseen.

Time always moves in the same direction, it always increases and never decreases: we always remember the past and never the future. This asymmetry of time is universal, from scales on Earth up to cosmological scales. We receive light that galaxies emitted long ago in the past and never receive light they emitted in the future. This time asymmetry is not reflected in the majority of physics laws which are time symmetric: they work in the same way if time is increasing or decreasing. In fundamental physics time is symmetric, and we attribute the cosmological arrow of time to very unusual initial conditions at the beginning of the universe. These conditions are so special that their probability is of order 1 in exp(10^90). Why the universe started in such an unlikely state is a question we have no answer for in cosmology. In this work we investigate whether the time asymmetry may already be present in the fundamental laws, which would avoid having to attribute it to very special initial conditions at the Big Bang. We construct models that simulate such a time asymmetry and the student will run simulations with these models from existing code. The code for the simulations is already in place, so the student can directly start working on it. The goal is to infer from the results of the simulations what are the properties of physics if its are fundamentally time asymmetric. This project is co-supervised by Prof. Andrew R. Liddle of I.A, and by Prof. Lee Smolin of the Perimeter Institute for Theoretical Physics in Canada.

This work will extensively investigate the tau reconstruction by means of new ML methods in two different environments at the CMS experiment at the LHC and at the new proposed Muon Collider. In the first case, data will be used to characterize tau lepton reconstruction. In the second case and due to the presence of the beam-induced background, a study of the tracking detector is also foreseen in order to maximize the exploitation of the time information in the silicon detector. Several options are possible, either measuring the time of each hit or having a dedicated layer in a strategic configuration. The algorithms will be studied on simulation and compared to CMS data. Using the new developed algorithms, the dedicated Higgs physics process will be reconstructed at CMS improving the current performance. They will be used to reconstruct the Higgs processes at the Muon Collider at the center-of-mass (CoM) energy of 3 TeV where the results will be compared to the those of the linear collider (CLIC). A CoM energy of 10 TeV is completely new and it has never been studied, and a brand new algorithm may be needed. Also at this energy the precision on Higgs boson couplings to tau leptons will be determined.

Central exclusive production (CEP) in high-energy proton-proton collisions provides a unique method to access a variety of physics topics, such as new physics via anomalous production of W and Z boson pairs, high transverse momentum (pT) jet production, top quark pairs, and possibly the production of new resonances. These studies can be carried out in particularly clean experimental conditions thanks to the absence of proton remnants. CEP of an object X may occur in the process pp → p+X+p, where ”+” indicates the “rapidity gaps” adjacent to the state X. Rapidity gaps are regions without primary particle production. In CEP processes, the mass of the state X can be reconstructed from the fractional momentum losses ξ1 and ξ2 of the scattered protons. At the LHC, the mass reach of the system X, MX, is significantly larger than at previous colliders because of the larger collision energy. The scattered protons can be observed mainly thanks to their momentum loss, due to the horizontal deviation from the beam trajectory. For the first time, proton-proton collisions at the LHC provide the conditions to study particle production with masses at the electroweak scale through photon-photon fusion. At the LHC energies in Run2 and in Run3, values of MX above 300 GeV can be probed. CEP processes at these masses have small cross sections, typically of the order of a few fb, and thus can be studied in normal high-luminosity fills.

The discovery of the Higgs boson in 2012 was a major step towards improving the understanding of the mechanism of electroweak symmetry breaking (EWSB). With the value of the mass of the H boson now experimentally measured, the structure of the Higgs scalar field potential and the intensity of the Higgs boson self-couplings are precisely predicted in the SM. 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. While measured properties are so far consistent with the expectation from the SM predictions, measuring the Higgs boson self-couplings provides an independent test of the SM and allows a direct measurements of the scalar sector properties. The self-coupling of the Higgs boson can be extracted from the measurement of the Higgs boson pair production cross section. 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.

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.

Intimately related to other areas of astrophysics and cosmology is the recently born field of gravitational wave (GW) astronomy. Crucial in the analysis of GW data is the input from numerical simulations in the form of waveform templates, which in turn carry the information from the physics in the strong field regime described by General Relativity (GR) via numerical simulations, from which the wave signals are extracted. As detector sensitivity increases, it needs to be matched by an improvement in the accuracy of the templates. One very promising and elegant way to get rid of finite-radius-extraction error is to numerically evolve the physical system of interest (e.g. a black hole binary) on hyperboloidal slices: spacelike slices that reach future null infinity, which corresponds to the endpoints of future-directed null geodesics and where global quantities of spacetimes such as energy or radiation are unambiguously defined. Conformal compactification, based on an idea by Nobel-laureate Penrose [1], is a suitable approach to the hyperboloidal initial value problem, further developed by Friedrich [2]. Formal divergences in the equations make numerical implementations of this problem challenging, but previous successful implementations encourage us to follow this promising path. The aim of this project is to generalise the existing free-evolution hyperboloidal spherically symmetric code [3] to axisymmetry, and so i) get closer to a full 3D hyperboloidal infrastructure to simulate binary coalescences and extract GW signals, and ii) couple the axisymmetric Einstein equations to physical content, such as scalar fields, the Maxwell equations and the Yang-Mills fields, to study their phenomenology in a scenario more general than spherical symmetry, and among them consider specially the candidates to fundamental fields. Additionally, the code can also be adapted to describe an Anti-deSitter (AdS) spacetime, and used to study collapse in axisymmetry. [1] Asymptotic properties of fields and space-times, Roger Penrose, Phys. Rev. Lett., 10:66–68 (1963). [2] Conformal Einstein Evolution, Helmut Friedrich, Lect. Notes Phys. 604 (2002), https://doi.org/10.1007/3-540-45818-2_1 [3] Spherical symmetry as a test case for unconstrained hyperboloidal evolution, Alex Vano-Vinuales, Sascha Husa and David Hilditch, Class.Quant.Grav. 32 (2015) 17, 175010, 1412.3827 [gr-qc].

One of the most important open questions in modern physics is how matter came to dominate over antimatter in the history of our universe. This question is intimately linked to the phenomenon of charge-parity symmetry violation (CPV), where particles interact at different rates compared to their corresponding antiparticles. So far, only a very small amount of CPV has been observed, which is insufficient to explain the matter-antimatter asymmetry of the universe. Neutrino oscillations, where neutrinos produced in a well-defined flavour are observed with a different flavour after travelling some distance, are the last remaining opportunity for large CPV to exist within the Standard Model (SM) of particle physics. The Deep Underground Neutrino Experiment (DUNE), currently under construction, aims to discover neutrino CPV by measuring oscillations of few GeV neutrinos over a distance of 1300 km. The experiment makes use of a novel detector technology, the liquid argon time-projection chamber (LArTPC) which allows for measurements with unprecedented precision. A core component of DUNE's innovative measurement strategy is the DUNE-PRISM moveable near detector which will allow for a data-driven analysis, with a reduced impact of the uncertainties related to the modelling of neutrino interactions. One of the main challenges toward the implementation of this groundbreaking analysis method is achieving the required precision in the models of the experiment's near and far detectors. The student will play a leading role in the development of the DUNE data-driven analysis, making use of advanced data analysis techniques, including machine learning. In addition, the student will analyse data taken by the DUNE prototype detector (ProtoDUNE) at CERN in order to improve the detector model based on calibration measurements and estimate the impact of detector model uncertainties on DUNE's sensitivity to discover CPV.

The asymptotic properties of spacetimes play a central role in many physical aspects of General Relativity (GR), in particular for the concept of gravitational radiation. One of the crucial concepts introduced for the realisation of the latter, was the use of conformal compactifications introduced in General Relativity by Roger Penrose to describe in a geometric way the notion of infinity. Arguably, the formulation that takes Penrose’s idea of conformal compactification --in conjunction with the theory of partial differential equations and the initial value problem-- to its ultimate consequences are, the Conformal Einstein Field (CEFE) equations introduced by H. Friedrich in [1]. These equations have been used for analytical purposes such as establishing (semi)-global non-linear stability results de-Sitter and Minkowski spacetimes and some partial global non-linear stability results for black hole spacetimes such as Schwarzschild-de Sitter [2]. Although these equations have been available since 1980 the numerical exploration of spacetimes using the CEFEs is still in its infancy compared with other formulations since they have not been systematically exploited as other formulations of GR. One of the alternatives to the CEFEs to reach the conformal boundary is the use of hyperboloidal foliations and scri-fixing techniques and more standard formulations of the Einstein Field Equations such as the Generalised Harmonic Gauge (EFE-GHG). These have also give fruitful results in combination with the weak null condition ---see [6]--- which can be exploited for numerical implementations [7] and for mathematical analysis [8]. By construction, hyperboloidal foliations reach the null-infinity but stays away from the region close to spatial infinity. The CEFEs on the other hand have access to this region via the construction of the so-called cylinder at spatial infinity. The latter has applications in terms of the calculation of asymptotic charges [4]. These methods, hyperboloidal and conformal, being complementary and grating access to the different regions of spacetimes can be exploited for the analysis of global properties of spacetimes by means of mathematical and numerical methods or a combination of thereof. ***The supervisor is currently working at University of Burgundy but will be joining soon Instituto Superior Tecnico Universidade de Lisboa under an FCT researcher contract*** [1] Friedrich H., On the regular and the asymptotic characteristic initial value problem for Einstein’s vacuum field equations, Proc. Roy. Soc. Lond. A 375 (1981) 169. [2] https://arxiv.org/abs/1506.00030 [3] https://arxiv.org/abs/1407.3317 [4] https://arxiv.org/abs/1608.05716 [5] https://arxiv.org/abs/1704.05639 [6] https://arxiv.org/abs/1812.06550 [7] https://arxiv.org/abs/1909.11749 [8] https://arxiv.org/abs/2101.07068

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

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

The observational evidence for the acceleration of the universe shows that canonical theories of gravitation, cosmology and particle physics are incomplete. The LambdaCDM model is a simple convenient approximation to a more fundamental theory, whose details or underlying principles are still unknown. Astrophysical facilities must search for, identify and characterise this new physics. The thesis will address this challenge, and specifically two questions: 1) Are the laws of physics universal? 2) What makes the universe accelerate? This relies on state-of-the-art high-resolution spectroscopy data from the ESPRESSO Guaranteed Time Observations, leading to the most accurate and precise such astrophysical tests, directly testing the Einstein Equivalence Principle and constraining dynamical dark energy. In parallel, the student will participate in Phases B and C of construction of the ANDES spectrograph, specifically by optimizing its cosmology and fundamental physics science cases, including the exciting prospect of the detection of the Sandage test signal. In addition to being part of ESPRESSO and ANDES, the student will be a member of the FCT Phi in the Sky project, funded until the end of 2025.

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 two running neutrino experiments, SNO+ and ProtoDUNE, and in auxiliary dedicated experiments.

The main goal of this project is to develop and test two innovative techniques to improve the sensitivity and background rejection capability of the next-generation XLZD dark matter and neutrino experiment. The first technique aims to improve the detector's light collection by using an efficient wavelength shifter embedded in the detector wall material. The second technique consists of applying compressed sensing to process the detector electronics output to reduce statistical fluctuations and improve the time resolution of the measured signals. Liquid xenon is currently well established in low-background experiments searching for new physics such as neutrinoless double beta decay (0νββ) or weakly interacting massive particles . It can also build neutrino detectors with ultra-high sensitivity based on coherent elastic neutrino scattering, with possible nuclear non-proliferation and reactor monitoring applications. Liquid xenon-based experiments are among the leaders in WIMP and 0νββ searches. The future XLZD experiment will combine searches for dark matter and neutrino physics, in particular, 0νββ. A major technical challenge for a future XLZD detector is the improvement of the detector's optical performance. In such large sensors, the photons will travel a considerable length before being detected, increasing the probability of being absorbed by impurities or scattered, affecting the scintillation's time profile. In addition, the overall light collection efficiency directly impacts the detector sensitivity and energy resolution, which is especially important for 0νββ search. In a modern liquid xenon detector, the internal walls are covered by PTFE (Teflon) sheets because of its high reflectance for the xenon scintillation light (at least 97% at 175 nm). Even then, only about 10% of scintillation photons are detected. Due to the above reasons, this fraction can be even smaller for XLZD if the current light collection technology is maintained. Also, the increase in the light collection time may compromise event discrimination based on analysis of the shape of the scintillation pulse. A promising way of overcoming these difficulties is transforming the light into a higher wavelength using a wavelength shifter. In the visible range, the reflectance of PTFE approaches 99%. At the same time, absorption and scattering in LXe/LAr are considerably smaller than those at 175 nm, allowing significant improvements in light collection and time response. The innovative method proposed in this project is to embed the WLS within the PTFE. Using a wavelength shifter inside liquid xenon and LAr particle detectors have been an active research topic for at least the last two decades. However, the main effort in this direction was associated with WLS surface deposition, which is unsuitable for PTFE in liquid xenon due to (i) poor adherence to fluoropolymer materials and (ii) solubility of common wavelength shifter compounds in LXe. We plan to test three alternatives for wavelength shifter embedding: PTFE/(wavelength shifter) mixture coating, mixing wavelength shifter with PTFE powder (granular PTFE), and diffusion of the WLS into PTFE at elevated temperatures. The obtained samples will be characterized for the embedded compound's overall efficiency and emission time profile. In parallel with this work, we plan to develop a technique for measuring the number of detected photons and times of their arrival with precision much better than that is currently achieved by the standard pulse processing algorithms for liquid xenon/argon detectors. Furthermore, we plan to develop a novel pulse processing method based on compressed sensing algorithms and characterize its performance as a function of the parameters of the photodetectors and the associated electronics. We also estimate the improvement this method would provide for the different types of physics analysis.

In this thesis the student will have the opportunity to develop Machine Learning algorithms with multivariate discriminators to search for and measure processes that suffer from large backgrounds at the LHC. Measuring the polarisation of the produced particles at the LHC, is one of the main objectives of the work plan. The student will have to test several networks and different architectures and is expected to train the algorithms in "Signal" and "Background" samples. In a first phase the student will appropriately train the methods of multivariate discriminators, with respect to the particle properties that are to be measured. At a later stage, these methods will be implemented in experimental analyses.

Our understanding of heavy baryons has expanded considerably in recent years with the discovery of many new states including charm and bottom quarks at the LHC. Heavy-baryon spectroscopy is now a cutting-edge area of research, and it is crucial to develop a theoretical understanding of such states from first principles in Quantum Chromodynamics (QCD). The goal of this project is to compute the spectrum of heavy baryons using functional methods in QCD, in particular the combination of Dyson-Schwinger equations and the three-body Faddeev equation which governs the behavior of baryons made of three valence quarks. These methods have been successfully employed in the light-baryon sector, and our aim is to extend them to charm and bottom baryons as well as for computations of their excitations and electromagnetic form factors. An important open question concerns relativistic effects which are crucial for light baryons, but recent studies suggest that relativity could also play in important role for charmed and even bottom baryons. As a key improvement, we will implement current progress in the calculation of QCD’s n-point correlation functions towards ab-initio calculations of heavy baryon spectroscopy and structure.

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

Neutrinos are very elusive particles which opened the window for physics beyond the Standard Model (SM) of electroweak interactions with the discovery of neutrino oscillations. With the confirmation of neutrino masses, there has been intensive activity in investigating the phenomenological consequences which stem from extending the SM such that neutrinos are massive. In this thesis several aspects related to neutrino physics may be covered. A more specific plan is to be decided together with the selected candidate and according to their possible interest in any neutrino-related topic.

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

Recent detections of binary neutron stars (NSs) mergers [1,2] opened a possibility to study their internal structure and equations of state (EoS) of matter at supranuclear densities [3] through the gravitational waves (GW) emitted during their coalescence. The finite size and internal structure of NSs alter a GW signal. Hence, GW models describing the binary neutron star coalescence incorporate the tidal deformations, which, once measured, allow us to constrain the internal composition of these objects. On the other hand, compact stars may accumulate a sizable amount of dark matter (DM) in their interior. In Ref. [4,5] asymmetric dark matter (ADM) captured by NSs was shown to be able to significantly impact stellar density profile and mass-radius relation. 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 a decrease, but to an increase of its visible gravitational mass. This analysis was performed for neutron stars composed of pure hadronic matter. However, due to the findings of Ref. [3] this seems to be an oversimplifying assumption. It is believed that in the core of compact stars matter could go through a phase transition from nuclear matter to a plasma of strongly interacting quarks. This type of star is called hybrid star. Depending on the properties of hadronic and quark matter EoSs the deconfinement phase transition may produce a visible feature in the GW signal and compact star properties. Thus, in Ref. [3] it was demonstrated that the tidal deformabilities and the I-Love-Q relation obtained for the GW170817 event support a strong phase transition to quark matter in the stellar interiors. Therefore, the study of DM admixed hybrid stars and their evolution with a further comparison with observational data will allow us to constrain the DM properties inside the compact stars and to place a limit on the DM sector of the Universe. The PhD project is focused on a study of the impact of DM on the properties of hybrid stars, their evolution, and stability against radial and non-radial oscillations. The main emphasis will be given to searches for the signatures of the presence of quark-gluon plasma in a core of compact stars and the effect of DM on it. The selected candidate will establish a bridge between astrophysics, nuclear physics and quantum chromodynamics. The thesis will be supervised by Prof. Ilídio Lopes, astrophysicist, from the CENTRA, Instituto Superior Técnico (Lisbon) and Dr. Violetta Sagun, theoretical physicist, from the University of Coimbra (Coimbra). 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] Paschalidis, V. et al., Phys. Rev. D 97, 084038 (2018). [4] Ivanytskyi, O. et al., Phys. Rev. D 102, 063028 (2020). [5] Karkevandi, D. R. et al., Phys. Rev. D 105, 023001 (2022).

From the experimental side, General Relativity (GR) has been successfully tested directly in the Solar System in its weak-field, slow motion regime. Binary pulsars, most notably the Hulse-Taylor system PSR 1913 C 16, allow for indirect tests beyond the Solar System. However, strong gravity tests are still scarse and gravity is tested poorly at the scale of galaxies and clusters, where Newtonian gravity breaks . This has led to the development of several modified theories of gravity to replace galactic dark matter. In fact, the discovery that the present expansion of the universe appears to be accelerated indicates that gravity may not be described by GR at large scales. To explain the cosmic acceleration, one needs to introduce an exotic negative pressure fluid, denoted dark energy, which constitutes approximately 70% of the energy content of the universe. Dark energy is thus an ad hoc solution to the problem of the present acceleration of the universe, and alternatives such as modified gravity have been explored. In fact, a plethora of modifications of gravity have been proposed as reliable alternatives to dark matter and dark energy. In the high-energy astroparticle physics regime, modified gravity could shed light on several outstanding problems in particle physics, such as the nature of dark matter, since its thermal production in the early universe may give rise to a relic density of the same order of magnitude of the present dark matter density. Particularly relevant in these scenarios could be the role played by modified gravity, as these theories predict a thermal evolution of the universe different with respect to one based on GR. More precisely, modified gravity predicts a modification/amplification of the expansion rate of the universe with respect to standard cosmology so that the thermal relics decouple with larger relic abundances. Consequently, the correct value of the relic abundance comes out from larger annihilation cross-sections. Other fundamental issues in the framework of modified gravity are related to the origin of the matter-antimatter asymmetry in the universe and Leptogenesis, as the matter-antimatter asymmetry is still an open problem of the particle physics and cosmology. Furthermore, mixing fields, vacuum fluctuations, neutrino oscillations, WIMPS, gravitational waves and the absolute value of the neutrino mass could be important tools to probe modified gravity. These issues will be explored in this project. The ultimate goal of the proposed research program is to devise viable modified gravity models that pass local tests, explain the dynamics of the Universe and are consistent with constraints from high-energy astroparticle physics, and thus offer a window into understanding the perplexing nature of the dynamics of the Universe and of gravity itself.

The fact that General Relativity (GR) is facing so many theoretical and experimental challenges, namely, the difficulty in explaining particular observations, the incompatibility with other well-established theories and the lack of uniqueness might be indicative of a need for new gravitational physics. Indeed, renormalization approaches to GR in the 1960s and 1970s clearly showed that counterterms must be introduced. These terms alter the theory significantly and transform the general relativistic second order field equations to fourth or higher order. This implies that extra degrees of freedom, in addition to the general relativistic spin-two massless graviton, need to be introduced. The corrections implemented by renormalization are at least quadratic in the curvature scalar invariant and were employed in inflationary models for the early universe. Considering a more general approach, when one tries to explore gravity from the high-energy regime and obtain low-energy physics, one does not recover GR. For example, adopting string theory as a full theory of quantum gravity, one gets a low energy limit that does not reproduce GR but instead provides a scalar-tensor theory of gravity. These latter theories were developed following initial suggestions by Dirac, Jordan, Fierz, and Thiery, culminating in the Brans-Dicke theory, which is the prototype of scalar-tensor theories of gravity. The original motivations for Brans-Dicke theory were rooted in the need to implement Mach’s principle, which is not fully incorporated in GR, in a relativistic theory of gravity. Indeed, dilaton fields and their nonminimal couplings to the spacetime curvature are unavoidable features of string theories, and are shared with scalar-tensor gravity. It seems, therefore, that first loop corrections or attempts to fully quantize gravity necessarily introduce significant deviations from GR and extra degrees of freedom. Thus, this motivates going beyond GR, from the high-energy theoretical point of view. In the high-energy astroparticle physics regime, modified gravity could shed light on several outstanding problems in particle physics, such as the nature of dark matter since its thermal production in the early universe may give rise to a relic density of the same order of magnitude of the present dark matter density. Particularly relevant in these scenarios could be the role played by modified gravity, as these theories predict a thermal evolution of the universe different with respect to one based on GR. More precisely, modified gravity predicts a modification/amplification of the expansion rate of the universe with respect to standard cosmology so that the thermal relics decouple with larger relic abundances. As a consequence, the correct value of the relic abundance comes out from larger annihilation cross-sections. Other fundamental issues in the framework of modified gravity are related to the origin of the matter-antimatter asymmetry in the universe and Leptogenesis, as the matter-antimatter asymmetry in the Universe is still an open problem of the particle physics and cosmology. Furthermore, mixing fields, vacuum fluctuations, neutrino oscillations, WIMPS, gravitational waves and the absolute value of the neutrino mass could be important tools to probe modified gravity. These issues will be explored in this project. The ultimate goal of the proposed research program is to devise viable modified gravity models that pass local tests, explain the dynamics of the Universe and be consistent with constraints from high-energy astroparticle physics, and thus offer a window into understanding the perplexing nature of the dynamics of the Universe and of gravity itself.

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.

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

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~10^9 M_sun) 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.

Muon tomography has several applications in engineering and geophysics. One of the main geometrical limitations of the muography technique arises from the fact that the atmospheric muons need to cross the objects from above. A laboratory building and a geological fault crossing a mine gallery were already observed with a non-optimized telescope. A next version should be able to allow for faster imaging of more complex structures, in view of applications in civil protection or follow up of construction of large underground infrastructures, as would be for example subway tunnels or the Lisbon water retention system.

Nuclei are the DNA of the cosmos [Woo03]. The understanding of the most basic characteristics that govern the strong, weak and electromagnetic interactions at the nuclear scale is of crucial importance to explain how our universe was formed and how it is evolving, how stars are born and die, and ultimately, how life came to exist. Powered by the energy released in its hot core, stars produce the largest bulk of natural appearing nuclei directly via nuclear fusion reactions [B2FH]. Beyond the iron natural abundance peak, heavier elements are produced predominantly via neutron capture reactions in the framework of the r-process [Thi11] and the s-process [Bus99]. Only a small fraction of stable isotopes located at the proton-richer side of the valley of beta stability, the so-called p-nuclei, cannot be synthesized through the previously mentioned processes. In the stellar environment provided by core-collapse and thermonuclear supernovae, the astrophysical p-process is the most established scenario for the production of the p-nuclei, which are synthesized via different photodisintegration paths starting on heavier nuclei and predominantly involving unstable nuclei [Arn03,Pig16]. In the framework of the present project, the PhD candidate will execute the first experiment that will determine the shape of the alpha-nuclear potential of radioactive isotopes (108,110)Sn located on the p-process nucleosynthesis path via the measurement of the elastic scattering angular distribution of alpha particles in inverse kinematics. This experiment will be possible thanks to the high intensity post-accelerated radioactive Sn beams available at the HIE-ISOLDE facility at CERN, combined with the recently developed technology of nuclear target production with high concentrations of helium nuclei [God16]. The supervisors of the present PhD program have led the international collaboration that recently proposed the innovative approach to the INTC (ISOLDE and Neutron Time-of-Flight Experiments Committee). The evaluation of the proposal was very positive, the INTC experts highlighted its scientific interest and its technical feasibility, and the full requested beam time was approved. The scheduling of the beam time is expected from July 2022 onwards. The scientific motivation of the proposed experiment lies in the fact that the uncertainties in the knowledge of the alpha-nuclear potential in the heavy regions of the nuclide chart constitute the main source of uncertainty in the production of the heavy stable p-nuclei [Rap06, Rau06, Rau16,Sim17]. Despite the various experimental efforts done over the past decades to reduce these uncertainties of this fundamental nuclear quantity (elastic scattering [Moh97,Zso01,Orn15], capture reactions online [Sch20] or through activation techniques [Hal12,Kis11]), these studies have always been limited to stable isotopes. Network calculations had to rely on the extrapolation of the theoretical models towards unstable nuclei [Arn03,Rau16]. The PhD candidate will analyse the first data available in unstable isotopes, opening the door to the reduction of the uncertainties in the modelling of the astrophysical p-process.  The present PhD program will be supported by the approved research project CERN/FIS-PAR/0009/2021. References: [Arn03] M. Arnould and S. Goriely. Phys. Rep. 384, 1 (2003) [B2HF] M. Burbidge, et al. "Synthesis of the Elements in Stars", Rev. Mod. Phys. 29, 547 (1957) [Bus99] M. Busso, R. Gallino, and G. J. Wasserburg, Annual Review of Astronomy and Astrophysics 37, 239 (1999) [God16] V. Godinho, et al.. ACS Omega, 1, 1229 (2016) [Hal12] Z. Halász, et al., Phys. Rev. C 85, 025804 (2012) [Kis11] G. Kiss, et al., Phys. Lett. B 695, 419 (2011) [Moh97] P. Mohr, et al., Phys. Rev. C 55, 1523 (1997) [Orn15] A. Ornelas, G. G. Kiss, P. Mohr, et al., Nucl. Phys. A 940, 194 (2015) [Pig16] M. Pignatari et al. International Journal of Modern Physics E 25, 1630003 (2016) [Rap06] W. Rapp, et al., Astrophys. J. 653, 474 (2006) [Rau06] T. Rauscher, Phys. Rev. C 73, 015804 (2006) [Rau16] T. Rauscher, et al., Monthly Notices of the Royal Astronomical Society 463, 4153 (2016) [Sch20] P. Scholz, H. Wilsenach, H. W. Becker, Phys. Rev. C 102, 045811 (2020) [Sim17] A. Simon, et al., J. Phys. G: Nucl. Part. Phys. 44, 064006 (2017) [Thi11] F.-K.Thielemann, et. al. Progress in Particle and Nuclear Physics 66, 346 (2011) [Woo03] S. Woosley, et al., "Nuclear data needs for the study of nucleosynthesis in massive stars", Nucl. Phys. A 718, 3 (2003) [Zso01] Zs. Fülöp, Gy. Gyürky, Z. Máté, et al., Phys. Rev. C 64, 065805 (2001)

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 commissioning DUNE runs. The project will initially focus on the analysis and evaluation of the system already put in place for the ProtoDUNE prototype at CERN, where the calibration systems are currently being deployed and with data taking expected to start in 2023. Using the experience and feedback from the ProtoDUNE data taking, it is then expected to carry out the development of the final systems to be deployed at the DUNE far detector.

Despite the many advances over the last decades in the understanding of neutrino properties and interactions, this elusive particle remains among the least understood of all fundamental particles. Nowadays, we know that neutrinos are central pieces in cosmology, particle, nuclear and astrophysics, and play a key role in the evolution of the Universe. Being the only fundamental fermion without charge, the neutrino also has the possibility of being a so-called Majorana particle, i.e., the neutrino can be its own antiparticle. The implications of this possibility are immense: if the neutrino is a Majorana fermion, one could explain the matter-antimatter asymmetry in the universe through a process of leptogenesis. Experimentally, the Majorana nature of neutrinos can be tested by searching for the neutrinoless mode of the extremely rare double beta decay. The rate of this process depends strongly on the neutrino masses and their ordering, with the inverted ordering region (m~15-30 meV) leading to half-lives of 10^26 - 10^27 yr. The search for this very rare process is currently one of the most active fields in neutrino physics, with over 10 experiments using a variety of candidate isotopes and technologies. This thesis will be integrated in the SNO+ experiment, that aims to observe this elusive decay through the decay of 130Te using liquid scintillator technology. The goal of this thesis will focus on the development of advanced event classification algorithms in order to improve the discriminating power of the experiment, further improving its sensitivity.

A huge number of neutrinos is expected to be produced at CERN's Large Hadron Collider (LHC) and yet, none of the LHC experiments has ever detected a neutrino. The Scattering and Neutrino Detector at the LHC (SND@LHC) will measure neutrinos of all three flavours (electron, muon and tau) originating from proton-proton collisions at LHC's Interaction Point 1 (IP1), where the ATLAS detector operates. SND@LHC is the most recent experiment at the LHC: it was installed and collected its first data in 2022. The detector employs a combination of detector technologies, including nuclear emulsions for identifying the neutrino interaction vertices, and scintillator detectors to identify muon tracks, electromagnetic and hadronic showers, and to identify events coincident in time with proton-proton collisions at the IP. By detecting neutrino interactions of all flavours at such high energies, SND@LHC will provide unique insights into the flavour structure of the Standard Model (SM) of particle physics. The main goal of this project will be to use the SND@LHC neutrino data to test the SM assumption whereby the three generations of leptons have exactly the same interaction strengths, the lepton flavour universality (LFU) hypothesis. Despite a few hints in existing data sets, there is currently no conclusive evidence of LFU violation. However, this hypothesis was never tested using neutrinos. The student will analyse the SND@LHC data to produce the first test of LFU using neutrinos by measuring the ratio of electron-neutrino to muon-neutrino interactions in the detector.

Integrated in sophisticated instruments at large scale facilities (LSF), 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), the neutron detectors enable to determine the positions of hydrogen and deuterium atoms in crystal structure, needed to reveal structural and dynamic aspects of the matter using neutrons as a probe, such as, e.g., of biological systems, nearly invisible using X-ray methods. However, the present state-of-the-art detectors cannot fully satisfy the tight requirements of the next generation instruments planned for the ESS and future spallation sources as well as of the upgrade programs of the existing large-scale facilities (LSF). For example, new instruments for reflectometry, small-angle neutron scattering (SANS) and macromolecular crystallography require detectors capable to provide simultaneously high detection efficiency, low gamma sensitivity, time resolution down to 0.1 µs, sub-millimeter spatial resolution and counting rate up to MHz/cm2. Ultra-high spatial resolution (~0.2 mm) is especially important for investigation of the structure of protein crystals of sub-millimeter size by neutron macromolecular crystallography. The capability to characterize samples of such small size is required since the growth of larger size crystals of biological macromolecules is very challenging. The same detector should also provide TOF capability with sub-microsecond time resolution, required to conduct high-precision wavelength-resolved measurements at the spallation neutron sources. Another example where the current neutron detection technologies are not adequate is in MIEZE neutron spin-echo spectroscopy, which is a novel method with ultra-high energy resolution for studies of ferromagnets, superconducting vortex lattices, and magnetic skyrmion systems. MIEZE requires neutron detectors with response time below 1 µs, very well-defined detection planes and high spatial resolution. The thesis programme is focused on the development of a novel detector concept, nRPC-4D, which offers four-dimensional readout capability (XYZ and time) and is intended for time-of-flight (TOF) neutron diffraction/reflectometry and energy- and time-resolved neutron imaging. The nRPC-4D concept combines two technologies: t-RPC (timing resistive plate chamber) invented in LIP for high energy physics applications and, to give RPCs the capability to detect thermal neutrons, B4C neutron converters enriched in boron-10 isotope developed jointly by the University of Linkoping and ESS. One main goal is to develop a detector demonstrator which can offer high time and spatial resolutions, good detection efficiency, high counting rate and low sensitivity to gamma rays. This PhD programme 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, FRMII and ESS), 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 programme implementation.

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

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

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

One of the major challenges of operating such detectors at the HL-LHC is the "pileup", or additional collisions occurring in the same proton bunch crossing as the collision of interest. By precisely measuring their time-of-flight, forward protons produced in these collisions can be correctly associated to the correct collision vertex, enabling rare photon-photon interactions to be reconstructed even at the maximum pileup foreseen for the HL-LHC. In order to fully resolve all collisions with forward protons, timing precisions of ~20ps or less will be of paramount importance, and enhance the sensitivity to these processes. During Run 2 of the LHC, proton fast timing detectors were already operated as a proof of principle, achieving resolutions of ~100ps with high efficiency. While these detectors were very resistant to radiation, they were limited, particularly by the TDC and related electronics, to timing resolutions of ~30-40ps per plane. For the HL-LHC, new technologies will be required to cope with the pileup, radiation, and event rates, both in terms of sensors and readout electronics. This project will help to address that challenge by exploring the latest developments in timing detectors and electronics, with the smallest possible segmentation and under extreme radiation conditions.

Polarized gamma-ray emissions over 1 MeV were never observed. The most energetic polarized emissions recorded were obtained by ESA INTEGRAL. By measuring the polarization angle and degree of linear polarization of the gamma-ray sources, it will be possible to obtain two additional observational parameters thereby allowing better discrimination between various models explaining the operation of emission sources. Polarimetric observations can provide important information about geometries, magnetic fields, composition and emission mechanisms in a wide variety of gamma-ray sources such as: pulsars, solar flares, active galactic nuclei, galactic black holes or gamma-ray bursts. AMEGO is a large satellite (1.2 tons payload) based on Si trackers, with a calorimeter composed by arrays of 3D CdZnTe (CZT) and of CsI scintillator detectors that will operate in the Compton (0.2 - 10 MeV) and pair conversion (10 MeV - 10 GeV) regimes. It should provide unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, AMEGO will open a new window on the non-thermal Universe. Our group will take part in the development of AMEGO scientific instruments by participating in the respective simulation and experimental testing. The AMEGO space mission should provide e+/e- pair production based polarimetry in the MeV and our group will be responsible for the polarimetric characterization of a small scale AMEGO prototype to be performed at the Duke University synchrotron accelerator and as well during a prototype for a balloon born experiment to be launched in Palestine, Texas.

In this PhD thesis proposal, we explore CP discrimination, in the associated production of top-quark pairs with generic scalar/pseudo-scalar and vector/axial-vector boson mediators, at the LHC. In addition to the Higgs boson, that may reveal a non Standard Model (SM) CP nature of the couplings to heavy quarks, these searches are also looking for hints of Dark Matter (DM) candidates, in simplified models with spin-0 and spin-1 particles, that act as mediators. Events from the associated production (ttX, X=spin-0, spin-1) of top quarks are searched for, in proton-proton collisions, at the Run3. A dedicated analysis for top quark pair production decaying to leptonic events with final states with at least one charged lepton and at least two jets from the decays of top quarks, is expected to be developed. Full kinematic event reconstruction is performed using a specific fitter which will be able to reconstruct the four momenta of the undetected neutrino(s), originated in the top quark decays. Following kinematic reconstruction, a search for specific angular distributions that are sensitive not only to the absolute value of the mediator CP couplings, but also to the signal (+ or -), is expected to be performed with the aim of discriminating, as well, the dominant backgrounds at the LHC from the signals under study. The mass range covered by the searches, start at low masses (order GeV) and goes to the high mass region (order TeV), passing through the Standard Model Higgs boson mass, used as a benchmark for the CP observables performance, developed during the course of this thesis. The use of Machine Learning algorithms for event classification, in particular to discriminate signals from background events, is also expected to be performed as, in the context of high energy physics, the use of ANNs in Deep Learning algorithms for event classification, has started to show particular promise in ttX with a completely new coverage of the CP parameter space. The impact on the signal sensitivity is to be quantified, using ATLAS data collected at the Run3, either as cross section and angular distributions measurements, in case of discovery, or by setting limits at 95% Confidence Level (CL), in case no New Physics is found. Monte Carlo generators, including MadGraph5_aMC@NLO with specific UFO models, are expected to be used to generate the different signals, at the RUN3 of the LHC.

The extension of the Standard Model of particle physics with new elementary particles and fundamental interactions seems to provide the best strategy to solve the Dark Matter Problem. Within this approach, the axion or their closest relatives—the axion-like particles (ALP) are among the most popular candidates proposed to explain dark matter. Such a class of particles will be tested by the forthcoming new generation of particle physics detectors by reaching previously untested regions of the particle dark matter parameter space. It will ultimately test such a strategy in the coming years. This PhD project uses stars as a cosmological tool to probe axion-like particles' basic properties. By computing stellar models evolving within different halos of dark matter and using asteroseismic observational data as a diagnostic tool, the candidate will be able to put constraints on many of the properties of these particles.

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. To address the open questions in the field, various extensions of the SM have been proposed, which typically predict the existence of new heavy particles with masses in the TeV scale. A vast program of searches by the ATLAS and CMS experiments at the LHC has, however, placed very strong constraints on the landscape of possible models for new physics. As a consequence, anomaly detection methods have been gaining ground, as part of a strategy to ensure a thorough and model-agnostic approach to new physics searches, expanding their potential and sensitivity to unexpected new signals. In this project, the student will take part in the ATLAS Collaboration program for new physics searches and explore the ATLAS dataset at the high energy frontier, including the wealth of data that is expected from the Run 3 of the LHC.

The PICOSEC detector [1] consists of a two-stage Micromegas [2] coupled to a front window that acts as a Cherenkov radiator coated with a photocathode. The time response of a single-cell PICOSEC prototype detector to single photons and to Minimum Ionizing Particles (MIPs) was extensively studied in laser and particle beams. Aiming at large area detectors, multi-pad PICOSEC prototypes were developed, which comprise segmented anodes divided into either hexagonal or square pads.

The expected neutrino spectrum at Earth, which is obtained by summing over the three flavors and integrating over all directions, has been recently calculated [1]. Results suggest that neutrinos may carry energies ranging from µeV up to PeV. While highly energetic neutrinos are probed in several experiments [2–5], the detection of neutrinos at ultra-low energies, i.e. in the range µeV − eV, remains so far elusive. Neutrino-plasma interaction plays a central role in astrophysical phenomena. It is well established that neutrinos release a large fraction of their energy to the plasma during the collapse of stars, making neutrino-plasma instabilities a pivotal ingredient in supernova explosions [6–7]. [1] E. Vitagliano, I. Tamborra, and G. Raffelt, Reviews of Modern Physics 92, 045006 (2020). [2] R. Bionta et al, Physical Review Letters 58, 1494 (1987). [3] S. Fukuda, et al., Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 501, 418 (2003). [4] J. Boger, et al., Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 449, 172 (2000). [5] F. Halzen and S. R. Klein, Review of Scientific Instruments 81, 081101 (2010). [6] L. O. Silva, R. Bingham, J. M. Dawson, J. T. Mendonça, and P. K. Shukla, Physics of Plasmas 7, 2166 (2000). [7] R. Bingham, J. Dawson, J. Su, and H. Bethe, Physics Letters A 193, 279 (1994). [8] A. Serbeto, J. T. Mendonça, P. K. Shukla, and L. O. Silva, Physics Letters A 305, 190 (2002).

The study of the Dark Matter (DM) phenomenology inside stars has already proven to be an important alternative way to study DM models. Its premise relies on the fact that Dark Matter particles in the vicinity of a star can be gravitationally captured by its massive gravitational field. There, DM particles will seldom interact with baryonic nuclei, serving as additional energy injection and transport mechanisms, which in some cases can lead to important effects in the stellar structure, causing considerable departures from the standard picture of stellar evolution. Using Asteroseismology, the study of stellar oscillations, as a diagnostic, we can constrain Dark Matter models leading to observables in contradiction with experimental observations.

Particle Physics and Cosmology are presently based on the construction of physical theories that are compared against observations to constrain model parameters. Despite the success of this paradigm, there is growing evidence of parameter tensions arising from the combination of observable properties and an increasing number of high-quality datasets. These tensions can be interpreted as opportunity windows for new physics, but that does not necessarily imply a deeper understanding at the more fundamental level. An alternative approach that could avoid tensions by construction is to let datasets to reveal their preferred laws, and then proceed with an interpretation at a more fundamental level envisioning the construction of consistent physical theories, without a priori assumptions. The overall objective of this project is the development, implementation and deployment of novel algorithms based on symbolic regression and machine/deep learning innovations emerging in the literature to infer data-driven expressions and seek model-independent information directly from cosmological data (see e.g. arXiv:1905.11481). In this project we will also study the application of these methods to derive the underlying profiles of halos, voids and the universe’s mean background density, and to confront these with theoretical predictions that rely on untested model assumptions about Dark Matter, Dark Energy and the Cosmological Principle.

The High Granularity Timing Detector will be an essential piece of the upgraded ATLAS detector for the high luminosity LHC phase. It will allow to suppress the background due to proton collision pileup, and so allow to achieve the ATLAS physics goals. This new detector will require a timing resolution of around 30 ps per charged particle track, obtained with the recent Low-Gain Avalanche Detector technology. These highly granular detectors will be read out using a new ASIC (ALTIROC) which is under development. The successful candidate will be integrated into the international team contributing to the development of the ALTIROC chip, a state of the art readout ASIC that will be at the heart of a new detector for the ATLAS experiment at the LHC. ALTIROC will need a very good timing resolution, of the order of 50 ps, and high charge sensitivity of about 2 fC, making this ASIC a challenging but crucial component of the experiment.

Heavy-quarkonium production in proton-proton collisions offers the best-known path towards the understanding of hadron formation within QCD. The production mechanisms are studied in the framework of non-relativistic QCD (NRQCD), a rigorous effective theory that exploits the factorization of short- and long-distance effects in the limit of small relative velocity of the quark and antiquark forming the bound state. The short-distance cross sections (SDCs), functions of the quarkonium kinematics, are calculable in perturbative QCD for each spin, angular-momentum, and colour (singlet or octet) configurations. Instead, the long-distance matrix elements (LDMEs), universal constants describing the non-perturbative evolution of the pre-resonance states to the observed mesons, must be determined through global fits of measured differential cross sections and polarizations. This means that crucial components of the theory predictions need to be determined by the data, implying a more elaborate theory-data comparison procedure than in most topics addressed in analyses of LHC data, where theoretical predictions can be directly compared to the measurements. The detailed understanding of quarkonium production implies performing simultaneous (global) fits of differential cross sections and polarizations, in particular because the measured cross sections depend on the polarization scenario assumed when computing the detection acceptances. Several papers have been published by the CMS collaboration reporting measurements of cross sections (or ratios) and polarizations of the J/psi, psi(2S), chi_c, Upsilon(1S), Upsilon(2S) and Upsilon(3S) quarkonium states. Most of these measurements were made using data collected with pp collisions at 7 or 8 TeV, in 2011 and 2012. While very interesting on their own (and the most precise until now), the impact of these results is limited by the relatively small size of the analysed event samples and by the restricted coverage in transverse momentum (pT). The data samples collected at 13 TeV (LHC run 2) correspond to a much larger integrated luminosity (more than 20 times that of the 7 TeV data), so that one can, for example, measure the J/psi polarization up to pT around 120 GeV (rather than around 25 GeV) and with much smaller uncertainties than the published results. This PhD thesis aims at providing state-of-the-art measurements of quarkonium cross sections and polarizations, including the S- and P-wave states from both the charmonium and bottomonium families, based on the CMS pp data collected at 13 TeV, already available for the final analysis steps (run 2) and/or being collected (run 3). Depending on several factors (specific interests of the student, time availability), the thesis will also include feed-down fractions and spectroscopy measurements. The student will be integrated in an experienced team and will be offered the opportunity of playing a leading role in these analyses, presenting the work in many CMS internal meetings, as well as in several international conferences and workshops.

Quantum computation and simulation is a new and promising paradigm to accelerate challenging computations. In particular, quantum computation is currently being explored in the context of High-Energy Physics, see for example the recent International Conference on Quantum Technologies for High-Energy Physics (https://indico.cern.ch/event/1190278/), held at CERN in November 2022. In this PhD project we aim at exploring the potential of quantum simulation for particle scattering processes. Namely, we will develop novel efficient methodologies for the non-perturbative calculation of Standard Model properties, with the goal to simulate scattering at colliders from first principles. This multidisciplinary doctoral project lies at the interface of effective field theories, perturbative and non-perturbative methods, and quantum computation and simulation.

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 such 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. They are detected through measurements of b-quark decays involving leptons. Such processes are highly sensitive to the presence of NP particles. The most favoured theoretical NP candidates addressing the anomalies would be LeptoQuarks (LQ) and new Gauge bosons (Z'). Even if those NP particles happen to be very heavy (and can thus not be produced directly in the LHC collisions), they do contribute as intermediary states (thanks to Quantum Mechanics) and their presence becomes experimentally accessible in measurements of these highly sensitive physics processes.

The Cosmic Neutrino Background is a relic of the Big Bang which was created when the Universe was just one second old. It is estimated that today its temperature is of roughly 1.95 K, with a very low energy spectrum ranging from 10^-6 to 10^-4 eV [1]. It is well established that neutrinos release a large fraction of their energy to the plasma during the collapse of stars, making neutrino-plasma instabilities a pivotal ingredient in supernova explosions [2-3]. They scientific case for this thesis will investigate this neutrino-plasma interaction to open a new unexplored window for the possible detection of low energy cosmic neutrinos. The goals for this project will be achieved through the theoretical designation metamaterial-made detectors. This work has an interdisciplinary scheme which will give to the appointed candidate the unique opportunity to deepen hot topics in both cosmology/high-energy physics and solid state physics. [1] B. Follin, L. Knox, M. Millea, Z. Pan, Physics Review Letters 115, 091301 (2015) [2] L. O. Silva, R. Bingham, J. M. Dawson, J. T. Mendonça, and P. K. Shukla, Physics of Plasmas 7, 2166 (2000). [3] R. Bingham, J. Dawson, J. Su, and H. Bethe, Physics Letters A 193, 279 (1994)

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. Over the years, experiments such as the Pierre Auger Observatory - dedicated to the study of ultra high energy cosmic rays - have shown that simulations have a deficit of muons with respect to what is measured. This is often called the EAS muon puzzle. The state of matter characterised by the deconfinement of quarks and gluons - the Quark-Gluon Plasma (QGP) - is created in ultra-relativistic heavy-ion collisions at the LHC. While its production was expected in high-energy nucleus-nucleus collisions, several hallmarks of QGP production have been observed in smaller collision systems, such as proton-nucleus and high multiplicity proton-proton. These observations suggest the possibility that tiny QGP droplets are also produced there. As such, the interaction of Ultra-High Energy Cosmic Rays (UHECRs) with the atmosphere atoms might attain favourable temperature and density conditions for the formation of the QGP. The presence of such state of matter will inevitably affect the resulting hadronic products, whose propagation through the atmosphere develops into an extensive air shower.

Ultralight bosons with masses below the eV scale have been predicted in a multitude of beyond Standard Model scenarios and their existence has also been proposed has a possible solution to the dark matter problem (see e.g. [1]). Quite interestingly, the existence of such particles could have a dramatic impact on the dynamics of black holes (BHs). For example, ultralight bosons can render spinning BHs unstable by extracting their rotational energy through a process known as BH superradiance [2]. This "superradiant instability" leads to a natural scenario where boson ''clouds'' can form around astrophysical BHs, leading to a pletora of signatures that could be detected both through gravitational-wave (GW) or electromagnetic observations (see [2] for a review on the subject). As a consequence of the universality of gravity, superradiant instabilities are a very generic phenomenon and should occur for any bosonic field propagating in a rotating BH spacetime, as long the field’s mass satisfies the right conditions for the instability to be effective. This phenomenon is more efficient when the boson’s Compton wavelength is of the order-of-magnitude of the BH’s horizon size, meaning that for astrophysical BHs with masses ranging between a couple of solar masses to tens of millions of solar masses, the existence of boson clouds could be used to detect or constrain bosons with masses in the range 10^{-20}-10^{-10} eV. However, the details of how the instability develops and its consequences for observations can be highly dependent on the presence of additional interactions, such as self-interactions or couplings to other particles (see e.g. [3,4,5,6,7]). The main goal of this project will be to understand how putative non-gravitational interactions can affect superradiant instabilites and related observables. This is an important task, especially given that most of the work related to superradiant instabilities typically assumes that non-gravitational interactions can be neglected. Not much is known on how exactly these interactions affect observables related to the formation of boson clouds around rotating BHs. This project aims precisely at making important contributions in this front. In particular we aim at exploring how non-gravitational couplings affect GW signatures from boson clouds around BHs. [1] L. Hui, “Wave Dark Matter”, Ann.Rev.Astron.Astrophys. 59 (2021) 247-289, https://arxiv.org/abs/2101.11735 [2] R. Brito, V. Cardoso, P. Pani “Superradiance”, Lect.Notes Phys. 971 (2020), https://arxiv.org/abs/1501.06570 [3] M. Baryakhtar et al, “Black hole superradiance of self-interacting scalar field”, Phys.Rev.D 103 (2021) 9, 095019, https://arxiv.org/abs/2011.11646 [4] T. Ikeda, R. Brito, V. Cardoso, “”Blasts of Light from Axions”, Phys.Rev.Lett. 122 (2019) 8, 081101, https://arxiv.org/abs/1811.04950 [5] E. Cannizzaro, L. Sberna, A. Caputo, P. Pani, “Dark photon superradiance quenched by dark matter” Phys.Rev.D 106 (2022) 8, 083019, https://arxiv.org/abs/2206.12367 [6] W. E. East, “Vortex String Formation in Black Hole Superradiance of a Dark Photon with the Higgs Mechanism”, Phys.Rev.Lett. 129 (2022) 14, 141103, https://arxiv.org/abs/2205.03417 [7] H. Fukuda and K. Nakayama, “Aspects of Nonlinear Effect on Black Hole Superradiance,” JHEP 01, 128 (2020), https://arxiv.org/abs/1910.06308

This thesis proposes a synergy between the areas of strong gravity, cosmology and particle physics in order to explore the FIP dark-matter paradigm. The deep-learning techniques necessary for these studies will be based on evolutionary optimization algorithms and computer vision methods recently developed both in the context of particle and gravitational wave identification. Contrary to the typical approach taken by the strong gravity community, this thesis aims at the construction of concrete particle physics models where ultralight DM particles can emerge either as pseudo-goldstone bosons or as vector bosons such that they can reveal themselves in the form of stable halos around compact astrophysical objects. However, such halos are only viable when the Compton wavelength of the field approximately matches the gravitational scale of the compact object. For the known astrophysical objects, such as black holes, whose mass ranges from 1-10^10 solar masses, this means that such bosonic particles must have masses between 10^{-10}-10^{-20} eV. The presence of an ultralight bosonic sector implies further bosonic particles that are not necessarily ultralight, although can still be dark. Furthermore, for models featuring neutrino mass generation mechanisms, a sterile neutrino can also become fermionic DM candidate with masses in the keV-MeV range. In this thesis, a catalog of models that can consistently predict light and ultralight bosons as well as sterile neutrinos will be constructed. These are extraordinary candidates to offer multi-component DM candidates which will be studied and confronted with data both from the gravitational and direct detection channels.

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.

The high-energy scattering of massive electroweak bosons, known as vector boson scattering (VBS), is a sensitive probe of new physics. VBS signatures will be thoroughly and systematically investigated with the large data samples available and those that will be collected in the near future at the LHC. Searches for deviations from Standard Model (SM) expectations in VBS will be performed with the goal of testing the Electroweak Symmetry Breaking (EWSB) mechanism. Current state-of-the-art tools and theory developments, together with the latest experimental results and the studies foreseen for the near future will be studied, implemented, and integrated in the research program. New data analysis strategies to understand the interplay between models and the effective field theory paradigm for interpreting experimental results will be developed with the goal of probing existing Beyond the SM (BSM) models.

You have heard about the LHC and CMS, one of the two 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 planned for 2029; 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. This is why the HGCAL is known as the 5D calorimeter and is a blueprint for future detector concepts. You will be part of a team of physicists and engineers working at the convergence of hardware, firmware, and software, with the goal of building the detector and providing electronics systems supporting all production and construction activities. As part of this team you will have the opportunity to touch upon questions such as machine-learned encoder-decoder architectures for real-time triggering, real-time monitoring and automated detection and low-latency reaction, synchronous and asynchronous control and data acquisition, or the integration of distributed computing architectures based on Zynq-like systems-on-chip. You will focus on the design of firmware blocks, implement them in different FPGA hardware as part of systems of different size and complexity, and commission them in large scale systems up to the full detector 100 FPGAs installed in the off-detector backend electronics. You will be expected to prototype multiple ideas both in simulation and on real hardware on the way to the final goal. Along the way, you will have have strong interactions with the software team so as to maximize the re-use of both firmware and software components. At the end of your time with IST and CERN, you will have made a mark by bringing an original computing concept to bear on the physics performance of this novel detector and have all the tools needed to work in large scale international real-time electronics projects.

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 thus provide a unique window into the early universe and possibly string theory. Recent progress in CMB and gravitational wave observations shows how some of these scenarios can in principle be constrained by high-resolution data, but also highlight several bottlenecks which make current constraints unreliable. To fully exploit the potential of ESA facilities such as the SKAO and LISA, one needs matching progress both in high-resolution HPC numerical simulations of defect networks and in the analytic modelling of key physical mechanisms underlying their evolution, especially additional degrees of freedom on the defect worldsheets. This thesis will address the latter, using a series of novel mathematical and statistical techniques, informed by the world’s most accurate defect simulations (being done by the supervisor’s team) to build upon the successes of the canonical VOS model of Martins & Shellard to develop a new generation of accurately calibrated analytic models for general defect evolution as well as for their astrophysical fingerprints, which is able to match the sensitivity of ongoing and future observational searches and yield reliable constraints. The student will be a member of an ongoing Paris-Porto-Cambridge exchange grant, and also of the FCT Phi in the Sky grant, funded until the end of 2025.

Gravitational-wave (GW) observations have an enormous potential to help solving long-standing problems in fundamental physics. In particular, in recent years it has become clear that these observations open unprecedented opportunities that could help us to characterise and identify dark matter [1]. Many proposals have been put forward about how GWs can gives us information about dark matter and its nature [1]. This project will be devoted to study one of such proposals. The main goal will be to study how the existence of ultralight bosons - particles with masses below the eV scale which have been proposed as strong dark matter candidates (see e.g. [2]) — could affect the GW emission from binary black holes (BHs). Ultralight bosonic particles are specially interesting in this respect because they can have Compton wavelengths as large as astrophysical BHs. This can lead to a plethora of interesting effects (see e.g. [2,3]) such as the formation of very long-lived structures, or “boson clouds” around spinning BHs that can be observed through several channels [3], including through GW observations. Recent developments have shown that, if existent, ultralight bosons could significantly modify the dynamics of binary BH systems leaving clear imprints in the GWs emitted the binary (see e.g. [4,5,6]). Within this context, in this project we will consider the so-called extreme-mass-ratio inspirals (EMRIs), binary systems in which a stellar-mass compact object, orbits a supermassive BH with millions of solar masses. These sources are expected to be detected by the future space-based GW detector LISA with extreme precision [7]. Most studies considering EMRIs evolving within boson clouds relied on non-relativistic approximations and simplistic assumptions about the orbital dynamics (e.g. circular orbits and neglecting the supermassive BH spin). Such approximations are clearly insufficient for an accurate description of these systems. This project will go beyond those simplifications by studying EMRIs evolving within bosons clouds using a fully relativistic setting. This is a necessary stepping-stone in order to be prepared for the future LISA mission. References: [1] G. Bertone et al, “Gravitational wave probes of dark matter: challenges and opportunities”, SciPost Phys.Core 3 (2020) 007, https://arxiv.org/abs/1907.10610 [2] L. Hui, “Wave Dark Matter”, Ann.Rev.Astron.Astrophys. 59 (2021) 247-289, https://arxiv.org/abs/2101.11735 [3] R. Brito, V. Cardoso, P. Pani “Superradiance”, Lect.Notes Phys. 971 (2020), https://arxiv.org/abs/1501.06570 [4] D. Baumann, H.S. Chia, R. Porto, “Probing Ultralight Bosons with Binary Black Holes”, Phys.Rev.D 99 (2019) 4, 044001, https://arxiv.org/abs/1804.03208 [5] D. Baumann, H.S. Chia, R. Porto, J. Stout “Gravitational Collider Physics”, Phys.Rev.D 101 (2020) 8, 083019, https://arxiv.org/abs/1912.04932 [6] D. Baumann, G. Bertone, J. Stout, G. M. Tomaselli, “Ionization of Gravitational Atoms”, Phys.Rev.D 105 (2022) 11, 115036, https://arxiv.org/abs/2112.14777 [7] S. Babak et al, Phys.Rev.D 95 (2017) 10, 103012 https://arxiv.org/abs/1703.09722

The study of the origin of solar and stellar magnetic cycles will significantly progress within the next decade, with the observational data obtained from present and future solar and astronomical missions. Examples are, for instance, the Parker Solar Probe (PSP) and the PLAnetary Transits and Oscillations of stars (PLATO). The PhD project's goal is two fold: (i) to test the validity of the solar dynamo theory in the context of other stars; (ii) to use the acquired knowledge of stellar magnetic activity to improve our understanding of the solar magnetic activity. Indeed, as a large amount of astronomical data will become available, it will be used to test a large region of the parameter space of the space weather, stellar magnetic activity and dynamo theories.

During the next two decades, the case for new particles as a possible solution to the Dark Matter Problem will face its moment of truth, with different Earth instruments and space missions reaching previously untested regions of the Dark Matter parameter space. Compact stars, notably Neutron Stars, are emerging as powerful tools in strategies to tackle the Dark Matter problem. For instance, if we hypothesize that heavy or light massive particles can constitute Dark Matter, these can form Dark Matter clouds within or around host compact stars. By doing so, these new stellar models will now account for non-trivial couplings between Dark Matter particles and Baryonic matter, resulting in the modification of the properties of the host star in such a way that will affect their measurable astrophysics properties.

Two-phase (liquid/gas) time projection chambers (TPCs) lead the search for dark matter (DM) particles with masses between ~1 GeV and ~10 TeV typical of new physics at the electroweak scale. This is a well established and scalable technology, having evolved from detectors with a few kg nearly two decades ago to the current 2nd generation (G2) multi-tonne detectors (LZ and XENONnT). A larger (G3) detector is nevertheless required to probe the remaining WIMP parameter space down to the irreducible neutrino “fog” and explore other models motivating lighter particles. The XLZD global consortium was recently formed, by merging members from the LZ, XENON and DARWIN collaborations, with the goal of designing and performing the required R&D towards such a detector. With 50-100 tonnes of xenon, it will be operating around the end of the decade and will serve as a Global Rare Event Observatory, with leading sensitivity to multiple DM candidates and many other rare physics phenomena, possibly including neutrinoless double beta decay (0𝝂ββ) in 136Xe. In this project the student will be directly involved in the development of technical innovations that will allow to expand the science reach of a G3 experiment and other future detectors based on noble liquids. These will include development and testing of a high-granularity scalable VUV-SiPM array as a possible alternative to the traditional photomultiplier readout used in such detectors. This array will be optimised for high spatial resolution (~100 µm), aiming to deliver track topology resolution at the 136Xe 0𝝂ββ decay energy (2.5 MeV), significantly improving the sensitivity of a G3 detector to this decay. Diffusion of the drifting ionisation dominates the spatial resolution in such a large detector; doping the xenon with light species (e.g. H2) can minimise this effect and will also be tested during this project. New electrode designs that allow to preserve the track information as the ionisation drifts (and focuses) past a gate grid and then collects onto an anode mesh will also be developed and tested. This project will be carried out in collaboration between LIP and UK groups. The measurements will be performed in a dedicated prototype xenon TPC constructed and hosted by Imperial College London. The student is expected to spend several time periods in the UK to work directly on the chamber. Moreover, the student will be integrated in the XLZD consortium, and will also study the impact of including the developed technologies in the design and science reach of the G3 experiment. During their visit, the student will join a cohort of PhD students at Imperial and benefit from training in high energy physics instrumentation and data-intensive analysis.

It is now well established that at several different cosmic scales, the dynamics of astrophysical objects seem not to comply with Newtonian and General Relativity theories of gravity if one considers only standard baryonic Matter. Such evidence led the scientific community to postulate what we call today Dark Matter: a generic gravitational term that can reconcile astronomical observations with General Relativity and standard quantum field theory. However, despite dark Matter being predicted to be four times more abundant than baryonic Matter and the primary pressure-less ingredient for the formation of our universe, little is known about its actual nature. Although Dark Matter can be made of a new kind of particles, as predicted by some quantum field theory (QFT) models, this is undoubtedly the most widely accepted proposal to explain the well-known dark Matter gravitational effects. However, more exotic possibilities have also been suggested within the last few years. One of the most interesting, in light of its relationship with the investigation of dark energy and comic inflation, and their roots in particle physics, is to consider Dark Matter as an effect resulting from modifications to Einstein’s General Relativity (GR). Indeed, one can even consider a QFT model that combines GR with the standard model of elementary particles. The target of this project is to go further along this line of investigation and to make an observationally based comparative study of the two approaches to dark matter mentioned above. We ask how will a GR extension affect the QFT dark matter model? Or put in a simpler way, how attractive is dark matter in a generalized GR model?

The research that will eventually be conducted to write a PhD thesis within this proposal involves using a seldom used mathematical technique in high energy physics, but only because the HEP community has not been aware. Otherwise, it has been employed in many domains of physics: e.g. including fractional calculus in atomic or solid-state (inc field theory representations) physics. The idea is presented in the Introduction of the review [1,2], but a fair summary can be found in many places, e.g., in D Torres's book [2]. The possibilities are pretty interesting as far as gravitational settings are concerned: see papers [ 1 ]. In this proposal, we will investigate (analytically, whenever possible, and numerically, see [1]) fractional differential calculus and subsequent equations that generalise well-known ones in gravitational physics. We aim to consider the equations governing gravitational collapse either classically or from a quantum (semiclassically) perspective with several fractional derivatives, not Riez's (as in [1]). This may allow making predictions and contrasts to establish which limits or ranges in the fractional derivatives are permitted, given known gravitational data. Fractional quantum gravity is very much in its infancy, and many cases need to be investigated. We will take either the gravitational collapse or deviations in gravitational radiation. Please note that, e.g. fractional uses of entropy and similar observables have found a correspondence in Barrow's proposals of entropy as fractal regions within suitable choices of parameters. Can it be those gravitational physics, if using fractional calculus, even as phenomenological toy models, will provide exciting and intriguing additional questions to address? Such a line is the course of the PhD research programme.

From the student is expected that he/she writes a PhD Thesis in the Field of physics Beyond the Standard Model, in particular Vector-like Fermions (VLF), based on original work published in the best international journals in the field, with focus on the quality and impact. The student is also required to participate in excellent international Schools and establish international contacts during Work-visits at CERN and other excellent Institutions and present his/her work at these events. The initial focus of the thesis will be on the study of models with VLFs, but the student will also be exploring models with multiple Higgs and others. The topics to be covered are, amongst other, the development and use of (new) concrete tools to test physics beyond the SM and explore NP models which are consistent with the Electro Weak Precision Measurements (EWPM) of the current and of future data, coming from LHC or others. In particular, we shall focus on very sensitive CP violation measuring parameters such as epsilon-K, epsilon’/epsilon or others, which will then severely restrict all kinds of various models and their content. In addition in our analysis of models, we will use other powerful tools based on weak-basis invariants. The CKM unitarity problem, is also an important problem which we will be addressing in the context of Vector-like Quarks (VLQ). At present, one of the main issues at the LHC is the search for new heavy fermions, e.g. quarks with masses beyond the top quark, as is the case of a heavy-top and which occurs naturally in models with VLQs in the up sector, or in the case of the leptons, the search for heavy Majorana neutrinos. With this in mind, we will be studying predictions for processes, possibly, to be witnessed at the LHC, as e.g. the decays of heavy-top T -> d W+. Thus, a strong interaction with experimentalists at LIP/CERN will be required. From the student it is expected that he/she acquires a very broad and deep formation in the fields of work proposed here.

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), which started operating in late 2021, is one of such detectors. Employing ten tonnes of liquid xenon, it contains a total of 630 kg of Xe-136 in its sensitive region. A preliminary study using simulated data showed that it could reach a half-life sensitivity of 1.06×10^26 years after 1000 days of operation, similar to the current best results. This study used conservative assumptions on the background assessment, energy resolution and background discrimination that can be significantly improved with real data. A next generation (G3) detector is already being planned, with a total mass up to 10x larger, which can lead to a half-life sensitivity 100x higher than LZ, leading to the confirmation (in case of an observation) or exclusion of the inverted hierarchy for the neutrino masses.

Ultra-relativistic nucleus-nucleus collisions at the Large Hadron Collider (LHC) provide a 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 [2]. Jets, collimated sprays of particles produced in the LHC collisions, are crucial probes to infer the properties of the QGP if the mechanisms of the energy loss and substructure modification are fundamentally perceived. The main goal of this project is the development of new observables for quantifying jet modifications in the QGP, following the proposal in [3] to measure average energy loss through the ratio of the transverse momentum (pT) in heavy-ion (HI) and proton-proton (pp) jets in the same quantile. This exploratory approach underlies any jet observable due to the relevance of selecting jets that were born alike. The standard R_AA (ratio between jets yields in HI and pp collisions at the same reconstructed pT bin), relying by definition on pT bin migration due to energy loss, is highly mis-leading because the history of the jets cannot be traced back. The project fits the priority of European Strategy for Particle Physics for quark matter research, which is the exploitation of the physics potential of colliding heavy ions at the LHC [4]. Accordingly, LIP and ATLAS are strongly committed with the Heavy Ion Program of the LHC. The ATLAS/LIP group signed the Letter of Intent of ATLAS in 1992 and is deeply involved in data analyses covering most studies of the LHC experimental programme and is strongly committed with detectors R&D as well. On the other hand, LIP has a long tradition in the QGP research, having played a key role in dedicated CERN experiments. We expect that this PhD project will further contribute to the strength of the laboratory in the field.

The data collected and analysed at the Large Hadron Colider (LHC) do not point to significant deviations from the Standard Model (SM). To distinguish background (SM) from possible new contributions, it is paramount to develop stringent tests of self consistency of the SM. The calculation of cross sections beyond leading order in perturbation theory is important to compare with experimental data provided by particle colliders. Whilst computations at next-to-leading order (NLO) are standard and can be done in most cases in a fully automated way, at next-to-next-to-leading order (N2LO) and next-to-next-to-next-leading order (N3LO) calculations are considerably more complicated and only a small number of processes have been computed so far. Beyond leading order, QCD cross sections, for instance, are typically split into several parts. At NLO there are virtual and real corrections, at N2LO there are two-loop virtual, virtual-real and double real corrections. Virtual corrections involve the calculation of loop diagrams and only the sum of all contributions leads to finite results. Such contributions are usually ultraviolet (UV) and infrared (IR) divergent and usually regularization dependent. Gauge invariant dimensional regularisation (DR) is the standard possibility but it has a few drawbacks. It is not compatible with the helicity method and other computational techniques that rely on working in the physical dimension. This results in cumbersome expressions in intermediate steps of a calculation. This is particularly troublesome in higher loop calculations as computational programs need a clear separation of UV and IR divergences in order to evaluate cross sections, for instance. Therefore regularization methods that work in the physical dimension of the model are promising. Also, as established by the Kinoshita - Lee - Nauenberg (KLN) theorem, there is a cancellation of IR divergences coming from the different sectors requiring that a significant part of the calculation must be done in analytical form. In this context, one is faced with the problem of choosing a regularization method to give sense to, otherwise, divergent quantities. A gain in efficiency could be depending on this choice, which justifies the interest in developing alternatives to the standard dimensional regularization scheme. In this project, we intend to tackle the infrared structure at N2LO in the Implicit Regularization (IReg) framework, which operates in the physical dimension and has been successfully applied to the computation of cross sections at NLO in perturbative QCD untangling UV and IR divergences. For example, processes of the type Higgs -> two gluons or Higgs -> heavy quark-antiquark pair, or two gluon production in quark-antiquark scattering are going to be considered in N2LO. As IReg operates in the physical dimension it is also a particularly useful tool for dimension specific theories, such as chiral and supersymmetric theories, where it has been largely applied. This line of research is supported by FCT Project CERN/FIS-COM/0035/2019. Bibliography: – “To d, or not to d : recent developments and comparisons of regularization schemes”, C. Gnendiger et al., Eur.Phys.J. C77 (2017) no.7, 471, and references therein; – “May the four be with you: Novel IR-subtraction methods to tackle NNLO calculations”, W. J. Torres Bobadilla et al. Eur.Phys.J. C81 (2021) no.3, 250, and references therein; “Two-loop renormalisation of gauge theories in 4D Implicit Regularisation: transition rules to dimensional methods”, A. Cherchiglia, D. C. Arias-Perdomo, A. R. Vieira, M. Sampaio and B. Hiller, Eur. Phys. J. C81 (2021) no.5, 468.

The research that will eventually be conducted to write a PhD thesis within this proposal involves using a seldom used mathematical technique in high energy physics, but only because the HEP community has not been aware. Otherwise, it has been employed in many domains of physics: e.g. including fractional calculus in atomic or solid-state (inc field theory representations) physics. The idea is presented in the Introduction of the review [1], but a fair summary can be found in many places, e.g., in D Torres's book [2]. The possibilities are pretty interesting as far as gravitational settings are concerned: see papers [ 1 ]. In this proposal, we will investigate (analytically, whenever possible, and numerically, see [1]) fractional differential calculus and subsequent equations that generalise well-known ones in gravitational physics. We aim to consider the equations governing cosmological evolution either classically or from a quantum perspective) with several fractional derivatives, not Riez's (as in [1,2]). This may allow making predictions and contrasts to establish which limits or ranges in the fractional derivatives are permitted, given cosmological and other gravitational data. Fractional quantum cosmology (or gravity) is very much in its infancy, and plenty of cases need to be investigated. We will take the early universe or late asymptotics. Please note that, e.g. fractional uses of entropy and similar observables have found a correspondence in Barrow's proposals of entropy as fractal regions within suitable choices of parameters. Can it be those gravitational physics, if using fractional calculus, even as phenomenological toy models, will provide exciting and intriguing additional questions to address? Such a line is the course of the PhD research programme.

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. Simultaneously, RHIC is preparing future Upgrades for the PHENIX Experiment, the new sPHENIX detector, that will increase its overall acceptance. These complementary measurements for the heavy-ion program 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 quantify the QGP properties and its time evolution.

The proposed project will focus in the pion- and kaon-induced Drell-Yan processes. The emergence of hadron mass (EHM) phenomenon, responsible for the quarks and gluons to acquire a running mass when confined in hadronic matter, remains a misterious aspect of QCD, the theory of strong interactions. Understanding the dynamic structure of the lightest of hadrons, pions and kaons, and compare it to the (much better known) structure of the proton, is key to clarify the EHM in QCD. In the absence of meson targets, pion- and kaon-induced Drell-Yan are the golden processes to access their hadron structure information, proposed to be measured by the new AMBER experiment. The already available data from the COMPASS experiment will be used to develop new optimised methods for a multidimensional analysis. The application of machine learning techniques to address different aspects of the analysis will be investigated. These studies were proposed and started in the recent past by members of the LIP group, being original both at COMPASS and AMBER. The first AMBER data with hadron beams to be taken in 2023 will require tuning, alignment and quasi-online analysis of the CEDARs information, a crucial step for the success of the physics Run. The student is expected to contribute significantly in this on-site effort, a necessary step to prepare later Drell-Yan measurements. Monte-Carlo simulations in the specific conditions of AMBER Drell-Yan will also be performed, to demonstrate the impact of the developed techniques. The main Drell-Yan measurement with positive pion beam is planned to happen in 2025. It will be preceded by several beam tests. These test beam data, COMPASS physics data and possibly the first Drell-Yan AMBER data shall be analysed in the context of this project. The student will be fully integrated in the portuguese LIP group participating in AMBER. Members of the group are main proposers of the AMBER and COMPASS Drell-Yan programs. The student will spend a significant part of the project time at CERN, integrating the AMBER analysis team, and will actively participate in the preparation, commissioning and data taking periods of the beam tests and physics Runs of AMBER. During his stays at CERN, close guidance and supervision to the student will be provided by Dr. Oleg Denisov, co-spokesperson of the AMBER Collaboration and main contributor to the Drell-Yan program, in coordination with the LIP supervisors.