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Lepton Flavour Universality
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 473 - Nuno Leonardo Co-Supervisor: 1796 - Alessio Boletti Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Ph.D in Physics at IST (Doutoramento em Física no IST) Typology: National
Summary
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. |
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Probing the primordial quark gluon plasma with heavy flavour
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 473 - Nuno Leonardo Co-Supervisor: 1788 - Yen-Jie Lee Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Ph.D in Physics at IST (Doutoramento em Física no IST) Typology: National
Summary
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. |
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Rare Higgs decays and couplings to quarks
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 473 - Nuno Leonardo Co-Supervisor: 1780 - Eliza Melo da Costa Co-Supervisor: 1777 - Sandro Fonseca de Souza Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Ph.D in Physics at IST (Doutoramento em Física no IST) Typology: National
Summary
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. |
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IDENTIFYING SIGNATURES OF HYBRID STARS
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 174 - Constança Providência Co-Supervisor: 230 - Márcio Ferreira Co-Supervisor: 2033 - TUHIN MALIK Host Institution: CFISUC - Centro de Fisica da Universidade de Coimbra Degree Institution: Universidade de Coimbra PhD Program: Doutoramento em Física Typology: National
Summary
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. |
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Signatures of ultralight bosons around black-holes: impact of non-gravitational interactions
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 347 - Richard Brito Co-Supervisor: 2078 - Chen Yuan Host Institution: CENTRA - Center for astrophysics and gravitation Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Physics Typology: National
Summary
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 |
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5D calorimetry at the HL-LHC: hard real-time embedded architectures for system testing and production
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society Supervisor: 145 - André David Co-Supervisor: 1787 - Nuno Roma Host Institution: CERN Experimental Physics Department Degree Institution: Universidade de Lisboa PhD Program: Ph.D in Electronics and Computer Engineering at IST (Programa Doutoral em Engenharia Electrotécnica e de Computadores do IST) Typology: Mixed Abroad-Institution: CERN
Summary
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. |
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A fast-timing high resolution detector concept with 4D capability for neutron science
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society Supervisor: 1712 - Luís Margato Co-Supervisor: 1719 - Andrey Morozov Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Universidade de Coimbra PhD Program: Doutoramento em Física Typology: National
Summary
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. |
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A New Approach to Study Jet Production in Pb+Pb Collisions at the ATLAS-LHC
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 92 - Helena Santos Co-Supervisor: 107 - José Guilherme Milhano Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Universidade de Lisboa PhD Program: Portugal – CERN PhD Grants Program Typology: Mixed Abroad-Institution: CERN
Summary
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. |
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Analysis of asymptotically flat and asymptotically de-Sitter spacetimes with conformal methods
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 1848 - Edgar Gasperin Garcia Co-Supervisor: 1847 - Alex Vano-Vinuales Host Institution: CENTRA - Center for astrophysics and gravitation Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: PhD Physics Typology: National
Summary
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 |
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Analytic Methods for Realistic Cosmic Strings and Superstrings
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 184 - Carlos Martins Host Institution: Centro de Astrofísica da Universidade do Porto Degree Institution: Universidade do Porto PhD Program: MAP-fis Typology: National
Summary
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. |
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ANDES: Reaching New Heights in Fundamental Cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 184 - Carlos Martins Host Institution: Centro de Astrofísica da Universidade do Porto Degree Institution: Universidade do Porto PhD Program: MAP-fis Typology: National
Summary
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. |
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Anomaly detection in the search for new physics with the ATLAS detector
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 1786 - Inês Ochoa Co-Supervisor: 55 - Patricia Conde Muino Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Physics Typology: National
Summary
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. |
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Antenna parton showers in an expanding QGP
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 107 - José Guilherme Milhano Co-Supervisor: 2087 - Korinna Zapp Co-Supervisor: 30 - Liliana Apolinário Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Doctoral Programme in Physics Typology: Mixed Abroad-Institution: Lund University (Sweden)
Summary
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). |
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Applications of modified gravity in high energy astroparticle physics and cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 466 - Francisco Lobo Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço Degree Institution: FCUL (Universidade de Lisboa) PhD Program: Astronomy and Astrophysics Typology: National
Summary
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. |
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Applying Fractional Calculus in Cosmology
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 114 - Paulo Moniz Co-Supervisor: 2080 - João Marto Co-Supervisor: 2083 - Seyed Meraj M. Rasouli Host Institution: CMA-UBI – Centro de Matemática e Aplicações Degree Institution: Universidade da Beira Interior PhD Program: Fisica 3º ciclo (CMA-UBI) Typology: National
Summary
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. |
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Applying Fractional Calculus in Gravitational Collapse
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 114 - Paulo Moniz Co-Supervisor: 2080 - João Marto Co-Supervisor: 2083 - Seyed Meraj M. Rasouli Host Institution: CMA-UBI – Centro de Matemática e Aplicações Degree Institution: Universidade da Beira Interior PhD Program: Fisica 3º ciclo (CMA-UBI) Typology: National
Summary
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. |
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Astrophysical tests of gravitational physics
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 184 - Carlos Martins Co-Supervisor: 619 - Filipe Mena Host Institution: Centro de Astrofísica da Universidade do Porto Degree Institution: Universidade do Porto PhD Program: MAP-fis Typology: National
Summary
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. |
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Atomic inputs for probing the r-process in kilonovae
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 1718 - Jorge Sampaio Co-Supervisor: 1946 - José Marques Co-Supervisor: 1955 - Gabriel Martínez Pinedo Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: FCUL (Universidade de Lisboa) PhD Program: Física Typology: Mixed Abroad-Institution: GSI Helmholtzzentrum für Schwerionenforschung
Summary
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 |
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Automation of Pre-processing of Synthetic Aperture Radar (SAR) Data with Machine Learning
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society Supervisor: 1786 - Inês Ochoa Co-Supervisor: 2088 - Joao Pinelo Silva Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Universidade de Évora PhD Program: Earth and Space Sciences Typology: National
Summary
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. |
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Axions in plasmas: axion-plasmon polaritons and the active generation of axions
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 1958 - Hugo Terças Host Institution: Instituto de Plasmas e Fusão Nuclear -IPFN Degree Institution: Universidade de Lisboa PhD Program: IDPASC - Physics Typology: National
Summary
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. |
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Beyond the physics we know – searching for new resonances in ATLAS with Higgs and vector bosons
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 484 - Ricardo Gonçalo Co-Supervisor: 1786 - Inês Ochoa Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Universidade de Coimbra PhD Program: Doutoramento em Física / PhD in Physics Typology: Mixed Abroad-Institution: CERN
Summary
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. |
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Birds of a feather: seeking the earliest high-energy events in the Universe at the high- and low-energy ends of the spectrum
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 234 - José Afonso Host Institution: IA - Instituto de Astrofísica e Ciências do Espaço Degree Institution: FCUL (Universidade de Lisboa) PhD Program: Astronomy and Astrophysics Typology: National
Summary
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. |
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Black-hole-induced vacuum transitions in Two Higgs Doublet Models
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 794 - Pedro Ferreira Host Institution: CFTC - Centro de Física Teórica e Computacional Degree Institution: FCUL (Universidade de Lisboa) PhD Program: Doutoramento em Física, Faculdade de Ciências, Universidade de Lisboa Typology: National
Summary
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? |
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Bridging theory to experimental data to unveil QGP time structure
Domain: Particle and Astroparticle Physics and associated scientific domains Supervisor: 30 - Liliana Apolinário Co-Supervisor: 2082 - Raghav Kunnawalkam Elayavalli Co-Supervisor: 107 - José Guilherme Milhano Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Instituto Superior Técnico (Universidade de Lisboa) PhD Program: Physics Typology: Mixed Abroad-Institution: Vanderbilt University
Summary
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. |
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Calibration control and monitoring of neutrino detectors
Domain: Technologies associated to the Portuguese participation at CERN and their transfer to society Supervisor: 1487 - Nuno Barros Co-Supervisor: 267 - Francisco Neves Host Institution: Laboratório de Instrumentação e Física Experimental de Partículas Degree Institution: Universidade de Coimbra PhD Program: Doutoramento em Física / PhD in Physics Typology: National
Summary
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. |