Graduate Seminar, 4th June

Speaker: Viktor Svensson

Title: Tensor Network techniques for many-body systems

Abstract: In quantum many-body systems of even moderate sizes, Hilbert space is far too large to fit on a computer. This makes numerical calculations a challenge. With the use of tensor networks, certain classes of quantum states can be efficiently represented and computed. In this talk, I will give an introduction to tensor networks and what they are good for.

 

Graduate Seminar, 28th May

Speaker:  Oleksandr Kovalenko

Title: Experimental tests of perturbative Quantum Chromodynamics

Abstract:  The Deep Inelastic Scattering and Drell-Yan processes can’t be directly calculated. The factorization concept assumes that the cross sections of these processes can be expressed as a convolution of parton distribution functions and fragmentation functions (FFs). These functions can’t be obtained from the theory and require an input form the experiment. The seminar will be focused on the techniques that are used to extract the FFs for pp and ep collisions. The comparison of theoretical estimates of FFs and the most recent experimental results on neutral meson spectra will be given.

Graduate Seminar, 21st May

Speaker: Erik Kofoed

Title:  Asymptotic Freedom at Finite Temperatures and Densities

Abstract: It is well known fact that the strong coupling constant in quantum chromodynamics (QCD) becomes weak at high energies which allows for perturbative calculations using Feynman diagrams. This is the phenomenon of asymptotic freedom. Much less clear is the status of asymptotic freedom at the early stages of a heavy ion collision where a bulk QCD medium is present. One difficulty is that there is, unlike in vacuum, no ‘best’ definition of what we mean with a coupling constant. The analysis is also complicated by the fact that a medium is characterised by several dimensionful scales, making the powerful scaling relations that can be used in vacuum not applicable

Thesis topic proposal

Dark matter: theoretical models, particle candidates and prospects of their experimental discovery

The Particle Theory Group led by Prof. Leszek Roszkowski invites applications for a 4- year PhD studentship at the National Centre for Nuclear Research (NCBJ). The studentship is funded by National Science Centre (Narodowe Centrum Nauki, NCN) within the Maestro grant “Dark matter: theoretical models, particle candidates and prospects of their experimental discovery”.

Continue reading Thesis topic proposal

Graduate Seminar, 14th May

Speaker: Artem Poliszczuk

Title: Searching for AGNs in the infrared data

Abstract: In the era of big data driven astronomy creating trustable catalogs of astronomical objects plays crucial role in observational cosmology. In particular, Active Galactic Nuclei (AGN) catalogs still cause many difficulties for the observers. In my presentation I will briefly discuss the general properties of different types of AGNs and focus on their identification in the infrared passbands due to the high AGN selection efficiency in this part of the spectrum.

Graduate Seminar, 30th April

Speaker: Oleg Shkola

Title: Searches for heavy stable charged particles at Compact Muon Solenoid experiment

Abstract: Many extensions of the Standard Model (SM) predict the existence of heavy, long-lived charged particles (HSCPs). These particles might have speed significantly less than speed of light and/or charge, not equal to ±1e. With lifetimes greater than a few nanoseconds, HSCPs can travel distances larger than the typical collider detector and appear stable like pions or kaons. Because particle identification algorithms at hadron collider experiments generally assume signatures characteristic of Standard Model (SM) particles, e.g., speed close to the speed of light and a charge of ± 1e, HSCPs may go unidentified. A further complication arises from the fact that HSCPs might be charged during only a part of their passage through detectors, further limiting the ability of standard algorithms to identify them. It is however possible to detect HCPs making use of their higher rate of energy loss via ionization (dE/dx) and longer time of flight to the outer detectors, in comparison with SM particles. During the seminar, results of dedicated searches, done at Compact Muon Solenoid (CMS) experiment on data collected during 2016 will be discussed.

Graduate Seminar, 23rd April

Speaker: Katarzyna Frankiewicz

Title: Search for dark matter induced neutrinos with the Super-Kamiokande detector .

Abstract: Indirect searches for dark matter are performed based on atmospheric neutrino data collected with the Super-Kamiokande (SK) detector in years 1996-2016. The excess of neutrinos from possible dark matter sources such as Earth and Galactic Center, compared to the expected atmospheric neutrino background is searched. Angular distributions and energy spectra as expected for signal and background are taken into account and various dark matter annihilation channels are considered. All event samples (fully-contained, partially-contained along with upward-going muons), including both electron and muon neutrinos, covering a wide range of neutrino energies (GeV to TeV) are used. The allowed number of dark matter induced neutrinos which can be contained in SK data so far is estimated. Obtained limits on dark matter induced neutrino flux from the Earth’s core are related to the limit on spin-independent WIMP-nucleon scattering cross section and compared against the results of direct detection experiments. In case of the Galactic Center analysis, the upper limit on the dark matter self-annihilation cross-section is derived.

Graduate Seminar, 16th April

Speaker: Jakub Sierchuła

Title: Dual Fluid Reactor – neuronics and fuel cycle modeling

Abstract: Dual Fluid Reactor (DFR) is a novel concept of a fast heterogeneous nuclear reactor which falls-off the classification of Generation IV International Forum (GIF). Its key feature is the employment of two separate liquid cycles, one for fuel and one for the coolant. In the DFR both cycles can be separately optimized for their respective purpose, leading to advantageous consequences: a very high power density resulting in cost savings, and a highly negative temperature feedback coefficient, enabling self-regulation without any control rods or mechanical parts in the core. During a seminar, reactor core model with new eutectuc U-Cr fuel composition and liquid lead as a coolant will be presented. The neutron flux density as a function of the energy in core was calculated, as well as fuel burn-up and effective multiplication factor/reactivity changes during reactor operation. In the reference design, fuel circulates at an operating temperature of 1300 K and can be processed on-line in a small internal processing unit utilizing fractionated distillation or electro refining. Except for heat or electricity generation, the unit with Dual Fluid Reactor could provide away some medical radioisotopes like Mo-99/Tc-99m.