Thesis topics in Physics (for October 2021, round 2)

  1. Gravitational lensing of the cosmic microwave background
    • Supervisor: dr. hab. Paweł Bielewicz
    • Description: Gravitational lensing of the cosmic microwave background (CMB) is a relativistic effect caused by the gravitational interaction of the CMB photons with matter inhomogeneities encountered during their travel from the last scattering surface to an observer. Reconstructed from correlated CMB anisotropy gravitational potential of the lensing structures projected along the line-of-sight gives a unique image of the formation of the large scale structure at high redshifts and enables testing cosmological models at large scales. On the other hand, generated by the lensing effect divergence-free component of CMB polarisation has to be precisely estimated and corrected to be able to detect primordial gravitational waves produced during the inflationary epoch. This PhD project will involve research on different aspects of the CMB gravitational lensing effect including developing and implementation of algorithms for estimation of the gravitational lensing potential, modelling and simulations of the effect, cross-correlations with galaxy and radio surveys and correcting CMB maps for the lensing effect. The PhD student will analyse publicly available data from the Planck satellite and other ongoing and near future CMB experiments. The cross-correlation studies will be realized within the framework of the Vera Rubin Observatory expected to begin observations in 2022. We seek strongly motivated PhD candidates with interest in cosmology who can demonstrate ability in programming and have experience in numerical methods.
    • Funding: NCBJ Fellowship
  2. BSM extensions with vector-like fermions confront long-lived particle searches
    • Supervisor: dr hab.Kamila Kowalska
    • Description: The pursuit for physics beyond the Standard Model (BSM) follows a twofold path. On the theoretical side, various BSM models can be proposed to address phenomena observed in nature. Among many extensions of the Standard Model, scenarios with vector-like (VL) fermions have long been enjoying a lot of interest. On the experimental side, a great effort was put in developing research strategies that go beyond the original LHC paradigm based on the missing transverse energy (MET). In particular, long-lived particle (LLP) searches show an increasing sensitivity in testing the parameter space of many BSM models in which the MET signature is absent. The aim of the PhD project is to perform a thorough analysis of a class of BSM extensions with VL fermions by confronting them with new data from various LLP searches. A crucial element of the project will be to develop a numerical tool to recast a wide set of LLP searches so that the experimental bounds they provide could be used in a user-defined model.
    • Funding: NCN Grant
  3. Gluon saturation in Quantum Chromodynamics at high-energy
    • Supervisor: dr hab. Tolga Altinoluk
    • Auxiliary supervisor: dr. Guillaume Beuf
    • Description: The microscopic theory describing the structure of protons and nuclei and the strong interaction binding them is Quantum ChromoDynamics (QCD). Even though the fundamental theory is known, it is extremely difficult to deduce from QCD the results of collision processes. This is due to the high level of complexity of the theory involving nonlinear interactions between gluons, which mediate strong interactions in a similar way as photons mediate electromagnetic interactions. When probed at very high energies, heavy nuclei and even protons appear as very dense clouds of gluons, with collective nonlinear interactions. This is the phenomenon of gluon saturation, which can be studied within the Color Glass Condensate effective theory (CGC). The main goal of this PhD project is to investigate the effects of gluon saturation in proton-proton and proton-nucleus collisions, as well as in Deep Inelastic Scattering (DIS), and derive higher order corrections of various types in order to improve the precision of theoretical predictions.Today, exploring QCD under extreme conditions, such as at high energy/density, is more important than ever due to its extensive exploration at the Large Hadron Collider (LHC) at CERN and at the future Electron-Ion-Collider (EIC) at Brookhaven National Laboratory.
    • Note: The standard admission process will be followed by a preselection procedure. The successful candidate will be working in close collaboration with the QCD groups in Universidade de Santiago de Compostela (Spain), University of Jyväskylä (Finland) and Ecole Polytechnique (France).
    • Funding: NCBJ Fellowship
  4. Search for nuclear chirality in low excitation energy states of odd-odd isotopes.
    • Supervisor: dr hab. Ernest Grodner
    • Description: Symmetries play a major role in the description of quantum many-body systems like heavy atomic nuclei which are composed of fermion particles. The quantum behaviour of such objects manifests itself through collective excited states decaying mostly via emission of gamma quanta. Experimental nuclear gamma spectroscopy is a tool to detect and trace these collective states and rare quantum phenomena taking place behind the scenes. In some cases these phenomena involve a process called the spontaneous symmetry breaking in atomic nuclei [1]. One of the most interesting and intensively studied symmetry of this kind is the chiral symmetry breaking in odd-odd nuclei [2, 3, 4] . The concept of chirality in the region of low nuclear excitation energies differs from chiral symmetry breaking in other fields of physics since it involves the time-reversal T operation instead of the space-inversion P. This makes nuclear chirality a unique phenomenon that, instead of parity, involves the time-reversal symmetry. The PhD project is focused on the experimental research of chiral-spontaneous symmetry breaking in atomic nuclei via lifetime measurements of their collective states. The obtained lifetime data describe the electromagnetic transition probabilities and electromagnetic matrix elements that are observables highly sensitive to occurrence of spontaneous chiral symmetry breaking in atomic nuclei. Lifetimes of such collective states are going to be measured in odd-odd La and Cs isotopes, initially involving EAGLE HPGe multidetector setup in beam of heavy ion cyclotron both located at Heavy Ion Laboratory of the University of Warsaw. The obtained results will be used for subsequent experiment proposals and for continuation of nuclear chirality research abroad.    
      [1]Stefan Frauendorf ”Spontaneous symmetry breaking in rotating nuclei”, Reviews of Modern Physics 73, 463 (2001)
      [2] E. Grodner at al., Physical Review Letters 97, 172501 (2006)
      [3] E. Grodner et al., Phys.Rev.Lett. 120, 022502 (2018)
      [4] Frauendorf, Meng Nuclear Physics A617, 131-147 (1997)
    • Funding: NCBJ Fellowship
  5. Physics of quark-gluon plasma
    • Supervisor: Prof. dr hab. Stanisław Mrówczyński
    • Description: Shortly after the Big Bang, hot and dense matter was in a state called the Quark-Gluon Plasma (QGP) where quarks and gluons are deconfined from hadron’s interiors. Studies of QGP, described by the Quantum Chromo-Dynamics (QCD), yields insights into the early Universe and strongly interacting matter under extreme conditions. Relativistic heavy-ion collisions offer a unique possibility to study QGP  in terrestrial experiments and to probe properties of the statistical QCD. A transient state of deconfined quarks and gluons is expected to occur at the early stage of nucleus-nucleus collisions. Currently, there are experiments at the Super Proton Synchrotron (SPS) at CERN, at Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) and at Large Hadron Collider (LHC) at CERN. There is a broad spectrum of theoretical problems to be studied in the context of quark-gluon plasma and relativistic heavy-ion collisions. The problems require various approaches from rather formal methods of quantum field theory to phenomenology of high-energy interactions, from quantum chromodynamics to kinetic theory and hydrodynamics.
    • Note: Partial NCN grant support
    • Funding: NCBJ Fellowship
  6. Longitudinal phase space linearization of PolFEL electron bunches with passive wakefield elements
    • Supervisor: Prof. dr hab. Jacek Sekutowicz
    • Auxiliary supervisor: Dr Jacek Krzywinski (SLAC, Stanford University)
    • Description: An efficiency of the Self Amplified Spontaneous Emission (SASE) process strongly depends on longitudinal emittance of electron bunches delivered to insertion devices by linear accelerators driving Free Electron Laser (FEL) facilities. While for large FELs like European XFEL in Germany, LCLS II in USA and SHINE in China one uses active high harmonic systems reducing nonlinear component of the bunch energy spread, smaller FELs can implement passive wakefield elements linearizing longitudinal emittance. The proposed PhD thesis will consist of theoretical studies, construction and test of a passive element suitable for the future implementation in the PolFEL superconducting accelerator to enhance efficiency of the coherent radiation generation.   
    • Funding: NCBJ Fellowship
  7. Studies of eta’ meson decays at BESIII experiment
    • Supervisor: dr hab. Andrzej Kupść
    • Description: The standard model of particle physics (SM) is not complete since it leaves out several questions unanswered, such as why there is more matter than antimatter in the universe. Therefore there should be new paricles not included in the SM. In addition to the direct searches for such particles at high-energy accelerators, a complementary method is to search for indirect effects they have on quantum fluctuations in vacuum. Such effects can be detected in precision low energy experiments such as muon anomalous moment (g-2) measurement or studies of violation patterns of fundamental symmetries such as charge conjugation (C) and parity (P). All low energy tests must include effects from light-hadron interactions (especially from the light mesons) which are difficult to calculate directly from the SM, since they involve strong forces at low energies. At the same time search for violation of the combined CP symmetry outside the known sources in the weak processes can be done using decays of light neutral mesons such as eta and eta’. The aim of the proposed PhD project is experimental study of eta’ meson decays using data collected at electron-positron experiment BESIII in China. The data set of 50 million of eta’ mesons allows one e.g. to improve determination of light meson interactions effects for g-2 value and to perform novel CP symmetry tests. The specific focus of the application are eta’ decay processes with four charged particles. The successful candidate will join new BESIII group at NCBJ.  
    • Funding: NCBJ Fellowship
  8. [Topic withdrawn]
  9. UV-complete BSM extensions with flavor and dark matter signatures
    • Supervisor: dr hab. Enrico Maria Sessolo
    • Description: The fundamental constituents of matter are described by the Standard Model of particle physics, one of the most successful theories in the history of science. Yet, there exist phenomena that are not predicted in this framework so that developing a theory “beyond” the Standard Model (BSM) and a sound strategy for its detection have become crucial endeavors. The energy scale of the new theory is unknown. It could be the extremely high energy of quantum gravity, which is well-motivated but very difficult to explore experimentally. Much closer to the energies we can probe, however, we sense the presence of particles possibly responsible for some of the signals that recently appeared in the LHCb detector, which are connected to the theory of “flavor.” And many theorists believe that just before our eyes may stretch a world of invisible, feebly interactive light particles, which could be at the origin of dark matter. The goal of this project is to draw connections between these different scales, from the UV to the IR, using modern techniques in quantum field theory, like the idea of asymptotic safety, and a systematic treatment of empirical data based on the latest numerical programs. By combining a variety of multi-scale inputs, the PhD candidate will participate in deriving unique predictions that can be tested in current and future experiments in particle and astro-particle physics.
    • Funding: NCN grant
  10. Study of dilepton production in relativistic nucleus-nucleus interactions at NICA facility
    • Supervisor: Prof. dr hab. Joanna Stepaniak
    • Auxiliary supervisor: Dr Damian Pszczel
    • Description: One of the most interesting features of strongly interacting particles is the formation, in relativistic heavy ion collisions, of a new phase of matter: the quark-gluon plasma. Pairs of leptons (e+e– and/or µ+µ–) do not participate in hadronic final state interactions therefore they can escape the hot and dense medium unperturbed, carrying valuable information about the early stages of QGP formation. The new facility NICA at the Joint Institute for Nuclear Research, that will become operational in 2023,  will be a very promising place for the study of dilepton production in heavy ions collisions. The successful applicant is expected to simulate the MPD (Multi Purpose Detector) and MCORD (Muon Cosmic Rays Detector – built in NCBJ) detectors response to relevant physical processes in order to optimise the  experimental conditions for  future data analysis. We plan to perform a two dimensional scan in energy and atomic number  of the colliding beams. The detector acceptances should be taken into account as well as a comparison with theoretical models. Those studies will benefit from supervisors’ experience in  similar analyses conducted in  NA61/SHINE experiment. The later is a fixed target experiment studying relativistic nuclear interactions at CERN SPS accelerator.
    • Funding: NCBJ Fellowship
  11. Proton charge-radius measurement using muon-proton elastic scattering
    • Supervisor: Prof. dr hab. Krzysztof Kurek
    • Auxiliary supervisor: Dr Paweł Sznajder
    • Description: The size of the proton is correlated with attempts to explain the confinement of quarks and gluons. Today there is a puzzle over that size; namely electron-proton scattering experiments and laser measurements of Lamb shift in muonic atoms are in a significant disagreement. This discrepancy may point to physics beyond the Standard Model or it could mean that low-Q2 scattering is more subtle than previously thought. In either case, solving the puzzle is crucial and the new measurements, preferably with new techniques, are of utmost priority. Such a new technique will be applied in the AMBER experiment using high-energy low-Q2 elastic muon-proton scattering at the M2 beam line of the CERN SPS starting in the year 2022. A high-precision measurement at low-Q2 realised with a high-pressure hydrogen time-projection chamber (TPC) can contribute to a solution of the puzzle, especially in view of different systematics of this approach compared to electron scattering.
    • Funding: NCBJ Fellowship
  12. Study of deeply virtual exclusive leptoproduction of single photons or mesons at COMPASS experiment
    • Supervisor: Prof. dr hab. Andrzej Sandacz
    • Description: Measurements of exclusive leptoproduction for processes such as deeply virtual Compton scattering (DVCS) and hard exclusive meson production (HEMP) provide information that is needed for phenomenological parameterisations of Generalised Parton Distributions (GPDs). The GPDs offer a novel description of the internal structure of the nucleon as a three-dimensional object, which goes beyond the standard one-dimensional description by the parton distribution functions (PDFs). In particular, GPDs allow to perform the “proton tomography”, i.e. to study a correlation between the fraction of nucleon longitudinal momentum carried by partons and their transverse spatial distribution. They also allow us to explain the role of the orbital angular momentum of partons in the nucleon and its contribution to the nucleon spin. The data that will be used for the proposed topic come from the COMPASS experiment at CERN. COMPASS is a fixed-target experiment measuring scattering of high-energy µ+ and µ- beams off hydrogen or polarised targets. Most of the data have been already collected, but more data taking is foreseen for 2021 and 2022.
    • Funding: NCBJ Fellowship
  13. Evolution of the large scale structure of the Universe from deep sky surveys
    • Supervisor: Prof. dr hab. Agnieszka Pollo
    • Auxiliary supervisor: Dr Anna Durkalec
    • Description: The evolution of the large scale structure of the Universe is among the most interesting of cosmological studies. These structures of the universe are mostly build of dark matter, which of course cannot be directly observed and its distribution is reconstructed based on the observations of galaxies. However, dark-matter galaxy connection is biased, and this bias evolves with redshift and different galaxy properties. Reversely, careful modelling of galaxy clustering allows us to reconstruct these underlying properties of the galaxy distribution, e.g. in the framework of the halo occupation distribution formalism (HOD). The successful candidate of this topic is expected to develop methods and codes – both traditional and machine-learning based – to measure and interpret galaxy clustering, and to apply them to perform high precision measurements in the present and forthcoming large and deep galaxy surveys, among them the future “Big Data” from the Legacy Survey of Space and Time (LSST) conducted by Vera Rubin Observatory.
    • Funding: NCBJ Fellowship
  14. Studies of x-ray spectroscopy techniques for the diagnosis of high-performance tokamak plasmas
    • Supervisor: dr hab. Jacek Rzadkiewicz
    • Auxiliary supervisor: Dr Karol Kozioł
    • Description: Fusion reactors are attractive candidates for ensuring efficient and clean large-scale energy production. The energy production with the use of thermonuclear reactions requires sufficiently high plasma temperatures, which becomes possible in tokamak laboratory conditions. Therefore, the ability to generate and maintain tokamak plasma with extremely high temperatures is one of the most important challenges for fusion research. The proposed studies will address the development of plasma temperature diagnostics based on the high-resolution x-ray spectroscopy. The main aim of the research will be in-depth analysis of the structure of X-ray spectra of metallic impurities arising in high performance tokamak discharges, in particular in the currently largest research fusion reactor – JET in Culham (UK). The studies should provide new quality data on key plasma parameters such as ion temperature and rotation velocity.
    • Funding: NCBJ Fellowship
  15. Studies of two-electron one-photon and forbidden transitions in x-ray spectra of highly-charged ions
    • Supervisor: dr hab. Jacek Rzadkiewicz
    • Auxiliary supervisor: Dr Karol Kozioł
    • Description: Atomic spectroscopy from many years is a powerful tool for study of processes occurring in the nanoscale. The High-Charged Ions (HCIs) constitute an attractive environment for studies of the nature of exotic atomic states and of mechanisms leading to their production. The study of the exotic Two- Electron One-Photon (TEOP) and so-called forbidden transitions permit both exploring the fundamentals of atomic physics (e.g. giving direct information on the HCI lifetimes or ionization mechanisms) and examining theoretical approaches used to analyse them. By comparing theory and experiment for high- energetic x-ray spectra of HCIs, one can evaluate contributions of various physical effects (such as Breit interaction, QED, and electron correlation effects) to the atomic structure of HCIs. So, theory can elucidate physics effects from experiment data. The topics of this PhD project focus on theoretical study on HCIs spectra by using MCDHF-CI method (Multi- Configuration Dirac-Hartree-Fock method with Configuration Interaction) and other appropriate ab initio computational methods, as well as on interpretation of experimental data provided by international experimental groups.
    • Funding: NCBJ Fellowship
  16. Search for new physics with displaced tau leptons and muons with the CMS experiment at LHC
    • Supervisor: dr hab. Michał Bluj
    • Description: The scientific goal of this doctoral Project is to search for phenomena beyond by the Standard Model (BSM) of elementary particles in final states with pairs of tau leptons and muons. The search will be conducted using data from proton-proton (pp) collisions at 13TeV, which will be collected by the Compact Muon Solenoid (CMS) experiment at CERN during the Run-3 of the LHC collider (2022-2024). The study will focus on the search for non-standard signatures with tau leptons and muons produced far from the pp collision vertex, so-called displaced tau leptons and muons. Such final states may arise from the decay of the hypothetical long-lived particles (LLPs) predicted by a number of extensions of the Standard Model. To date, a number of searches for long-lived particles have been performed, some with the CMS detector, but one of the still unexplored signatures are the final states with displaced tau leptons. Among models where such signatures are expected are those in which the LLP couples to particles of the Standard Model by mixing with the Higgs boson, or in which the LLP is a heavy neutral lepton, i.e. a heavy neutrino. The results of the search proposed in the Project may significantly contribute to setting strict limits to the proposed BSM scenarios or to the discovery of new particles. One of the challenges of the Project is a demanding reconstruction of tau leptons. Tau leptons decay in about 1/3 of the cases into lighter charged leptons, electrons or muons, (and neutrinos) or into hadrons (and a tau neutrino) in the remaining 2/3 cases. Charged leptons from tau lepton decays are generally indistinguishable from directly produced leptons, while decays to hadrons can be effectively used to identify tau. The difficulty in reconstructing tau decays into hadrons is the background from hadrons copiously produced in pp collisions. This background must be suppressed as much as possible while maintaining high efficiency of identifying tau. On the other hand, leptonic tau decays, due to the relatively low production rate of leptons in pp collisions, are helpful (in conjunction with hadronic tau decays) in the selection of events containing tau-tau pairs. The first stage of the planned research is to develop algorithms for the reconstruction of the signal characteristic for hadronic decays of tau leptons produced outside the interaction point as such algorithms are currently not available in the CMS experiment. The next step is to build efficient algorithms for triggering based on newly developed tau reconstruction algorithms in combination with similar muon algorithms. The next step is to construct the analysis, i.e. define the event selection, background estimation methods and statistical analysis of the results. A particularly demanding step is the background estimation, which we expect is largely due to instrumental effects that are difficult to simulate. This requires the development of methods to determine the background with the use of control samples of pp collision data. The exact definition of these methods and samples with estimation of related systematic uncertainties are important parts of the Project.
    • Funding: NCBJ Fellowship