Physics thesis topics (for February 2020)

  1. 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
  2. Exploring the production rate of very heavy nuclei in high-K states
    • 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!
    • Funding: NCBJ Fellowship
  3. Search for super-stable high-K super-heavy isomers
    • Supervisor: dr. hab. Michał Kowal
    • Description: 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. We are going to discuss the influence of the odd nucleons on the hindrance mechanism in alpha decay process.
    • Funding: NCBJ Fellowship
  4. Testing cosmological models using observations of type Ia supernovae
    • Supervisor: dr. hab. Paweł Bielewicz
    • Description: Type Ia supernovae are used in cosmology as standard candles enabling to measure distances at very high redshifts. Observations of stronger than expected dimming of the high-redshift supernovae allowed for discovering acceleration of the Universe expansion and establishing the Lambda Cold Dark Matter (LambdaCDM) model. The Large Synoptic Survey Telescope (LSST) is predicted to observe few millions supernovae during its ten-year survey over a large fraction of the sky and a broad range of distances. It is two orders of magnitude more than total number of supernovae observed so far. With such large number of observations it will be possible to constrain the standard cosmological model with unprecedented precision. We will be able also to perform statistical tests of distribution of the supernovae in the sky and measure cross-correlation between observed supernovae and other cosmological probes. The proposed PhD project will mainly be realized within the framework of the LSST project expected to begin observations in 2022. In the first phase of the PhD project the successful applicant will develop and optimize methods of testing cosmological models using simulations of the LSST supernovae observations. The next step will be application of these methods to the first data from the LSST.
    • Funding: NCBJ Fellowship
  5. Phenomenology of vector-like extensions of the Standard Model
    • Supervisor: prof. dr hab. Leszek Roszkowski
    • Auxiliary supervisor: dr Kamila Kowalska
    • Description: There are many reasons to believe that the Standard Model is not the final theory of nature, but we still do not know which of many beyond the Standard Model scenarios is the true one. One of the possibilities considered in the literature is to extend the Standard Model by vector-like fermions. The topic of the PhD project is to investigate phenomenological properties of such scenarios by means of dedicated numerical tools and taking into account large amount of experimental data from the LHC, flavor physics experiments and dark matter searches.
    • Funding: NCN grant
  6. New samples for the analysis of neutrino oscillations in the T2K experiment
    • Supervisor: dr hab. Justyna Łagoda
    • Description: T2K is an experiment searching for neutrino oscillations and measuring cross-sections of neutrino interactions. The upgrade of T2K experiment includes changes in the Far Detector (Super-Kamiokande) and its calibration and reconstruction which allow to improve the detector performance and allow to better study the neutrino oscillations, aiming for observation of the CP violation for neutrinos. The student will work on the search and definition of the new samples of neutrino interactions for the oscillation analysis taking into account the present upgrades of the experiment. The candidate will collaborate with an international team of physicists; will present his/her work at local meetings in Poland and at collaboration meetings in Japan. It is possible to stay for training period in Japan during the doctoral studies.
    • Funding: NCN grant
  7. Study of neutrino interactions on correlated nucleon pairs in the T2K experiment
    • Supervisor: dr hab. Justyna Łagoda
    • Auxiliary supervisor: dr Joanna Zalipska
    • Description: T2K is an experiment searching for neutrino oscillations and measuring cross-sections of neutrino interactions. This project will be focused on investigations of interactions with correlated nucleon pairs, which are still not well known. The candidate will work on the analysis using (anti)neutrino data collected by the near detector of the T2K experiment and will contribute to work dedicated to the upgrade of that detector. The upgrade of the near detector is planned to be finalized in 2021. The student will contribute to the understanding of detection of low momentum particles. The candidate will collaborate with an international team of physicists; will present his/her work at local meetings in Poland and at collaboration meetings in Japan. It is possible to stay for training period in Japan during the doctoral studies.
    • Funding: NCN grant/NCBJ Fellowship
  8. Quantum gravity, deformed symmetries and phenomenology
    • Supervisor: prof dr hab. Jerzy Kowalski-Glikman
    • Co-supervisor: prof. dr hab. Wojciech Wiślicki
    • Description: Quantum gravity, deformed symmetries and phenomenology Description: There are good reasons to believe that quantum deformed relativistic symmetries might be relevant in description of physics at sub-Planck energies, where some effects of quantum gravity origin are still present. Such effects might be observable in current and future experiments. Of particular interest are deformations of discrete symmetries operators C, P and T, that are are modified by terms dependent on four-momenta and the deformation parameter kappa. Given large number of the existing and planned experimental studies on conservation of these symmetries, experimental data can be incorporated to find limitations on kappa. In this PhD project we are planning to investigate the quantum gravitational origin of continuous and discrete symmetries and the resulting effective and phenomenological models. These models will be then applied to study various phenomena in cosmology and particle physics, like the theory of bariogenesis and testing CP, T and CPT invariance in decays of heavy flavours s, c and b.</p> <p>This PhD project will contribute to the EU COST action CA18108 QG-MM “Quantum gravity phenomenology in the multi-messenger approach” and the successful candidate will be able to take part in this action activities (conferences and workshops).
    • Funding: NCBJ Fellowship
  9. Statistical analysis of galaxy properties – how estimates of different galaxy properties are limited by the photometric coverage of the spectra?
    • Supervisor: dr hab. Agnieszka Pollo
    • Auxiliary supervisor: dr Katarzyna Małek
    • Description: Estimation of the main physical properties of galaxies is often based on joint analysis of the light emitted from stars and dust and study of the full spectral energy distribution. Unluckily, photometric surveys usually do not include measurements from the full spectral coverage from the ultraviolet (young stars) to the far-infrared (dust). In this project, we will study the limitations of the new and near-future surveys (for example LSST) to recover the true and unbiased values of the main physical parameters of galaxies. Which properties can we obtain with small uncertainties, and which are going to be impossible to estimate? A PhD student involved in this project can possibly become a member of large projects including Herschel Extragalactic Legacy Survey (HELP), LSST, LOFAR, VIPERS and others.
    • Funding: NCBJ Fellowship
  10. Machine learning techniques for present day and future big cosmological surveys
    • Supervisor: dr hab. Agnieszka Pollo
    • Description: Machine learning techniques are now becoming more and more popular in astronomy, being applied to various tasks, from classification or clustering of data to regression-based parameter reconstruction or deep learning based image analyses. With increasingly rising sizes of sky surveys, application of automated techniques is no more a matter of choice but necessity. The successful candidate will develop and apply machine learning methods for reconstruction of galaxy properties and cosmological studies from present-day and future big sky surveys, with the aim to prepare a methodology for the coming data from big sky surveys, including the Large Synoptic Survey Telescope.
    • Funding: NCBJ Fellowship
  11. Vector Boson Scattering with the CMS experiment at the LHC
    • Supervisor: dr hab. Michał Szleper
    • Description: Vector Boson Scattering is an important class of processes which probe the properties of the Higgs boson as well as of the intermediate weak bosons W and Z. They are a crucial test of the Standard Model of particle physics and allow for indirect searches for new physics in the most general theoretical framework of Effective Field Theories. The project will involve analysis of data collected by the CMS experiment during Run II of the LHC. The successful applicant is expected to participate in the analysis of the same-sign WW scattering process, with both W bosons decaying into leptons. This will include full implementation of the novel “clipping” method to derive the most correct limits on new physics, and/or development of techniques to tag different W polarizations from the data. The project will include also work on the muon trigger system within the Warsaw CMS group.
    • Funding: NCBJ Fellowship
  12. Search for hadron exotic states in LHCb experiment at CERN
    • Supervisor: prof. dr hab. Wojciech Wiślicki
    • Auxiliary supervisor: Dr Dmytro Melnychuk
    • Description: From the very beginning of the research in hadron physics the attention was focused on hadrons with properties that look unusual in contrast to the rest of the spectrum. Such hadrons are usually called exotic, however the concept of exotic is changing with time. Nowadays to exotic hadrons the states different from conventional meson and baryons are assigned, such as tetraquarks and pentaquarks. In the latest 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 candidates for 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 the year 2021. The PhD project concerns the search for new and interpretation of the nature of already observed exotic hadrons.
    • Funding: NCBJ Fellowship
  13. Assessment of the source term
    • Supervisor: prof. dr hab. Wacław Gudowski
    • Description: HTGR fuel has very low fission product release during operation and even in case of an accident. Nevertheless the fission products accumulating in the primary system during the whole lifetime of the reactor form the source term that can be released in the environment in case of a break in the primary containment. It is important for safety to have an assessment of the global activity that can be released into the environment. But even if measuring the circulating activity is easy and if some of the plated out activity could also be measured (e.g. the activity plated out in the Intermediate Heat Exchanger – IHX), part of the activity in the primary circuit remains inaccessible (e.g. activity adsorbed in graphite). The objective of the PhD is to define a strategy for assessing continuously the global activity in the primary system through a limited number of accessible measurements (e.g. only the circulating activity or the circulating activity + the plated-out activity in the IHX). For this purpose, existing data and models on fission product transport, plate-out and lift-off should be revisited and the possibility to get new data on existing HTGR test reactors (HTTR, HTR-10) should be investigated, to improve the knowledge on the distribution of fission products in the primary system. An assessment of the uncertainty of the evaluation of the global activity should be made. The result of this PhD will be very useful for the licensing of the FOAK reactor.
    • Funding: PhD4Gen program
  14. Investigation of alternative option of HTR configuration dedicated for mixed fuel cycle with thorium utilization
    • Supervisor: prof. dr hab. Jerzy Cetnar
    • Description: HTR is a versatile reactor in terms of utilised fuel. As thorium-uranium cycle can be an attractive alternative to uranium-plutonium one it has its challenges due to lack of U233 in nature. Th-U cycle in existing solutions involves thorium irradiation in a reactor blanket and then its reprocessing after discharge from the reactor. As the thorium fuel reprocessing brings many challenges an alternative options that are based on once-through cycle or applying simplified separation (fission products removal only) will be examined in terms of reactor core design and separation feasibility.
      Funding: PhD4Gen program