Physics thesis topics (for February 2021)

  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 photon deflection angles 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 also realized within the framework of the Large Synoptic Survey Telescope experiment 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. New generation of gravitational wave detectors and its potential for testing cosmology and fundamental physics.
    • Supervisor: prof. dr hab. Marek Biesiada
    • Description: First detections of gravitational waves (GWs) by LIGO/Virgo collaboration opened a new window on the Universe. Following this ground-breaking achievement, GW community proposed a third-generation underground detector called the Einstein Telescope, which will have an order of magnitude better sensitivity than current detectors. This means that it would be able to probe three orders of magnitude greater volume of the Universe leading to an unprecedented statistics of GW sources originating at high redshifts. Moreover, there are advanced actions toward launching space-borne detectors LISA and DECIGO probing GW spectrum at low frequencies inaccessible from the ground. Their reach will be even bigger than the ET. Such concerted multifrequency coverage will elevate GW physics from weekly or monthly detections to a high-statistics era allowing high-precision astronomy and confronting the General Theory of Relativity with a plethora of experimental tests. Based on the Monte Carlo simulations of realistic forecasts of future GW data, the sucessful applicant will study the following issues: i) cosmological tests based on standard sirens using only observables obtainable from GW signals alone (i.e. without knowing the redshift of the source, but knowing its luminosity distance), ii) observational signatures of gravitational lensing of GW signals at low frequencies, iii) joint multifrequency observations of inspiralling binaries from the space and from the ground and their potential to directly probe the expansion of the Universe and testing theories violating Lorentz invariance.
    • Funding: NCBJ Fellowship
  3. 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 using several techniques 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 to continue 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
  4. Alpha-particle clustering in medium mass nuclei
    • Supervisor: dr hab. Nicholas Keeley
    • Description: The degree of alpha-particle clustering in medium mass nuclei, e.g. Ca and Ar isotopes, is a topic of considerable current interest. Sophisticated large-scale modern shell model calculations are able to predict the structure of these nuclei and can quantify the probability of formation of alpha-particle clusters through the medium of the alpha-particle spectroscopic factors, Sα, quantities which can be extracted from experimental measurements and thus compared with the theory, providing an important validation of the calculations. Unfortunately, the Sα are not observables, that is to say they cannot be directly measured, and must be extracted from direct reaction data using a model of the reaction process. This makes the empirical Sα extracted from data “model dependent” quantities and, despite over 40 years of effort, they remain notoriously poorly determined. This project aims to use new data to be obtained at the Heavy Ion Laboratory of the University of Warsaw to carry out comparative studies of different heavy-ion induced alpha-particle transfer reactions – (12C,8Be), (16O,12C), (20Ne,16O) and (24Mg,20Ne) – to attempt to establish a coherent, consistent picture of the alpha-particle clustering in the ground states of stable Ca isotopes. The successful candidate will be expected to carry out all aspects of the setting up and running of the experiments and the data reduction. A major part of the work will consist in modelling the reaction data using state-of-the-art direct reaction codes to extract the Sα. These will be compared with the results of modern large scale shell model calculations. Part of the goal of this work will be to attempt to establish whether one of the reactions in particular is best suited to these studies. Opportunities to participate in experiments at radioactive ion beam facilities elsewhere will also be available, in particular at GANIL, France, and possibly also ISOLDE, CERN, Switzerland, TRIUMF, Vancouver, Canada, and EXOTIC/SPES, Legnaro, Italy.
    • Funding: NCBJ Fellowship
  5. Search for super-stable super-heavy high-K isomers.
    • Supervisor: dr. hab. Michał Kowal
    • Description: Superheavy elements are extremely unstable systems with very low production cross sections. Existing experimental facilities limit the possibilities for discovery of new nuclides to those synthesized with the cross sections above 100 fb what is possible currently in selected laboratories, actually only in two of them, i.e. in DUBNA and in RIKEN. As the creation of new elements is a very difficult task as a parallel or additional line of study one could try a search for new, long-lived metastable states of already known heavy nuclei. Evaluation of probability of synthesis such heavy nuclei in high-K states via fusion evaporation reactions will be the main topic of this thesis – never done before! Due to small structural overlap and strong centrifugal effect transition between non-analogical states are excluded. Different excitation energies of a high-K configuration in parent and daughter nucleus seem than particularly important for a hindrance of the alpha-decay. This, together with their relatively low excitation suggests a possibility that they could be isomers with an extra stability – five and more orders of magnitude longer-lived than the ground states. This in turn would mean that chemical studies of such exotic high-K sates would be more likely than for quite unstable ground states. In this thesis, for the first time, we plan to include into two- and four-quasi particle states additional odd particle effect with this we are going to discuss the influence of the odd nucleons on the hindrance mechanism in alpha decay process.
    • Funding: NCBJ Fellowship
  6. Deep and machine learning methods for searching for optical counterparts to gravitational wave events
    • Supervisor: prof. dr hab. Andrzej Królak
    • Auxiliary supervisor: dr Adam Zadrożny
    • Description: One of the hottest topics in today’s astronomy is searching and analyzing optical counterparts to gravitational wave events. Still there is only one such event observed, which is GW170817 / AT 2017gfo. It was observed during LIGO-Virgo Observing Run O2, which lasted 6 months and had one event that might plausibly produce optical counterpart. During O3 the third observing run there were more than 10 event that might have optical counterpart, but yet none was found. In order to make search more successful in upcoming LIGO-Virgo O4 science run (2022+) we would like to develop a strain of machine learning/deep learning methods for optical follow-up. The developed methods would be tested on TOROS collaboration telescopes during LIGO-Virgo O4 Observing Run. There is a possibility to expand scope of the project to electromagnetic data from POLAR-2 and LSST.
    • Funding: NCBJ Fellowship
  7. Understanding inner structure of Active Galactic Nuclei
    • Supervisor: dr. hab. Agnieszka Pollo
    • Auxiliary supervisor: dr K. Hryniewicz
    • Description: Typical spectral analysis of an active galactic nuclei allows to derive global parameters of the system: supermassive black hole mass oraccretion disc luminosity. Direct interpretation of spectral components suggest rather localized compact emitting regions. However this reasoning does not conform results of variability studies nor simulations nor physical models describing line emitting region which suggest extended source of radiation reprocessing. We propose to resolve this discrepancy with a new way of spectral analysis, which is fully motivated by AGN physics and reveal the direct cause of observed differences among sources. Successful applicant is going to co-develop new methods of data analysis and its implementation in massive data processing procedures. Results will help to understand observed spectral properties of active galaxies and explain phenomenological unification scenarios of AGN population on the ground of physics. We expect that this effort greatly improve calibration of quasar observations in cosmological application thus will be important beyond its field. PhD student will have a chance to participate in the international collaboration and support big projects like LSST with her/his results.
    • Funding: NCBJ Fellowship
  8. Longitudinal phase space linearization of PolFEL electron bunches with passive wakefield elements
    • Supervisor: dr hab. Jacek Sekutowicz
    • Auxiliary supervisor: Dr. Jacek Krzywinski,
    • 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
  9. Direct photon production in relativistic heavy-ion collisions measured in the Alice experinet at the CERN Large Hadron Collider
    • Supervisor: prof. dr hab. Teodor Siemiarczuk
    • Description: The direct photons are the unique probes carrying information about the structure of hadrons and characteristics of the hot partonic matter – the quark-gluon plasma (QGP). The latter is a special state of matter consisting of quarks and gluons no longer confined into hadrons. The QGP was presumably the state of matter existing in the Universe some tiny fraction of a second after the Big Bang. After subsequent cooling, the QGP changed to hadrons which we observe today. The QGP can be created artificially in the laboratory in the small Big Bangs in high- energy heavy-ion collisions when the hadronic matter is heated to the temperature of about 150 MeV. The ALICE experiment, one of the four large CERN experiments, is the only one dedicated to the study of the QGP. ALICE consists of 18 detectors. One of them is the unique highly granulated photon spectrometer with high spatial and energy resolution in a wide dynamical range. The photons interact via the electromagnetic force and, due to the weakness of the electromagnetic interaction compared to the strong interaction between hadrons, their free path in the strongly interacting medium is relatively large. They escape from those hot-spots of the hadronic matter with their momenta unchanged providing us with the „snapshots” of the matter in the moment of their production. The aim of this PhD Thesis will be to single out the direct photons from those stemmed from the particles decay, compare their production with the perturbative QCD predictions for hard interactions of partons and seek for the direct thermal photons emitted from the hot fireball of the quark-gluon plasma.
    • Funding: NCBJ Fellowship
  10. Study of Vector Boson Scattering in the same-sign WW process at the CMS experiment
    • Supervisor: dr hab. Michał Szleper
    • Description: Vector Boson Scattering (VBS) processes belong to the most important tests of the Standard Model of particle physics.  They probe Higgs couplings to vector bosons W and Z, as well as triple and quartic couplings between bosons themselves.  In addition, scattering of longitudinally polarized vector bosons provides a direct glimpse of the mechanism of electroweak symmetry breaking.  In recent years the CMS and ATLAS experiments at CERN have observed for the first time the VBS processes at a level roughly consistent with Standard Model expectations, but more data is crucial in order to place better limits on Beyond Standard Model physics.  The successful applicant will participate in the analysis of the same-sign WW scattering channel in the leptonic W decay mode from CMS data collected during LHC Run 3.  He/she is expected to fully implement and develop the “clipping” technique to derive limits interpretable in the language of Effective Field Theories and to develop techniques to tag W/Z polarizations.  The project will also involve technical work on the CMS muon trigger system as part of the Warsaw CMS group activities.
    • Funding: NCBJ Fellowship
  11. QCD in the Electron-Ion Collider Era
    • Supervisor: prof. dr hab. Lech Szymanowski
    • Auxiliary supervisor: Dr. Guillaume Beuf
    • Description: Our understanding of protons and neutrons, or nucleons—the building blocks of atomic nuclei—has advanced dramatically, both theoretically and experimentally, in the past half century. It is known that nucleons are made of fractionally charged “valence” quarks, as well as dynamically produced quark-antiquark pairs, all bound together by gluons, the carrier of the strong force. A central goal of modern nuclear physics is to understand the structure of the proton and neutron directly from the dynamics of their quarks and gluons governed by the theory of their interactions, quantum chromodynamics (QCD). The designed Electron Ion Collider (EIC)  is the instrument that can answer many of these fundamental questions. The topics of this PhD project focus on either theoretical or phenomenological investigation of some processes which will play a key role on EIC physics studies and on the interpretation of the results of the ongoing experiments at LHC, JLAB, RHIC and COMPASS. Successful candidate will have the opportunity to collaborate with world-known physicists from France, Spain and USA.
    • 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