Thesis topics in Physics (for February 2022)

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. 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, simulations of the effect, cross-correlations with galaxy and radio surveys and, necessary for detection of primordial gravitational waves, correction of CMB maps for the lensing effect. The PhD student will analyse 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 C. Rubin Observatory expected to begin observations in 2023. We seek strongly motivated PhD candidates with interest in cosmology who has experience in programming and data analysis.
   • Funding: NCBJ Fellowship
2. Multifrequency gravitational wave detections – strong lensing signatures and cosmological applications
   • 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.
   • Funding: NCBJ Fellowship
3. 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. Due to small structural overlap and strong centrifugal effect transition between non-analogical states is 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 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 for 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 the alpha decay process.
   • Funding: NCBJ Fellowship
4. Direct photon study in relativistic heavy-ion and proton-proton collisions  measured in ALICE experiment at the CERN Large Hadron Collider
   • Supervisor: Prof. Dr hab. Teodor Siemiarczuk
   • Auxiliary supervisor: Dr Podist Kurashvili
   • Description: The direct photons are the unique probes carrying information about the structure of hadrons and the characteristics of the hot partonic matter – the quark-gluon plasma (QGP). The latter is a state of matter consisting of quarks and gluons no longer confined into hadrons. The QGP was presumably the state of matter that existed 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, one of the four large LHC CERN experiments, is the only one dedicated to the study of the QGP. ALICE consists of 18 detectors. One of them is the unique, finely granulated photon spectrometer with high spatial and energy resolution in a wide dynamical range. Photons interact via the electromagnetic force and, because of the weakness of the electromagnetic interaction compared to the strong one between hadrons, their free path in the strongly interacting medium is relatively large. Photons 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. This PhD Thesis aims to single out the direct photons from those originated 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. The successful candidate will travel to CERN to participate in measurements with the ALICE detector on the Large Hadron Collider beam.
   • Funding: NCBJ Fellowship
5. 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 with NICA 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. The candidate will have the opportunity to compare his/her Monte Carlo study with real data from fixed target NA61/SHINE experiment at CERN SPS accelerator. Those studies will benefit from supervisors’ experience in similar analyses conducted in this experiment.
   • Funding: NCBJ Fellowship
6. Search for excited and multiquark hadrons at LHCb experiment at CERN
   • Supervisor: Prof. Dr hab. Wojciech Wiślicki
   • Auxiliary supervisor: Dr Dmytro Melnychuk
   • Description: From the very beginning of research in hadron physics attention was focused on hadrons with properties that look unusual in contrast to the rest of the spectrum. Such hadrons are called exotic. Nowadays, to exotic hadrons the states different from conventional meson and baryons are assigned, such as tetraquarks and pentaquarks, including recently found doubly-charmed tetraquark. In recent years more than twenty states with charm and beauty quarks not fitting into conventional description has been found and labeled as X, Y, Z, P. Among them there are several tetraquark and pentaquark states. LHCb experiment at CERN contributed significantly to observation and interpretation of these states and the search is ongoing with already collected data and with data which collection is going to resume from 2022 with much higher intensity and better accuracy. The PhD project concerns the search for new and interpretation of the nature of already observed exotic hadrons.
   • Funding: NCBJ Fellowship
7. BSM physics searching via development of displaced muon trigger for the CMS experiment
   • Supervisor: Dr hab. Piotr Zalewski
   • Auxiliary supervisor: Dr Karol Buńkowski
   • Description: The quest for Beyond Standard Model physics signatures is strongly represented in the LHC physics program. CMS is one of two omnipuprose LHC detectors. Warsaw CMS group is composed of physicists from NCBJ and University of Warsaw as well as electronics engineers form Warsaw Technical University. We are involved in searches for BSM physics and we contribute to the CMS muon trigger by being responsible for a part of it. The proposed topic will allow the successful candidate to learn and contribute to state of the art triggering system and take part in its improvement which should allow to search for BSM signatures which are hardly accessible with the present setup.
   • Funding: NCBJ Fellowship