"Theory of Particle Physics and Cosmology" Seminar
2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025
2020-03-19 (Thursday)
join us at 12:15 
Mikołaj Misiak (IFT UW)[ON-LINE] B -> Xs gamma$ @ NNLO and feasibility of B -> Xc l nu @ NNNLO
https://meet.google.com/iie-rdtz-ddo?hs=122 (the seminar takes place on-line only)
Strengthening constraints on new physics from the B -> Xs gamma branching ratio requires improving accuracy in the measurements and the Standard Model predictions. To match the expected Belle-II accuracy, Next-to-Next-to-Leading Order (NNLO) QCD corrections must be calculated without the so-far employed interpolation in the charm-quark mass. I am going to summarize the current status of such calculations. Moreover, I will describe recent improvements in estimating non-perturbative contributions to BR[B -> Xs gamma], and the resulting update of the SM prediction. Finally, feasibility of determining the NNNLO QCD corrections to the inclusive semileptonic B -> Xc l nu decay is going to be discussed.
The slides are available at https://www.fuw.edu.pl/~misiak/misiak.html
2020-03-12 (Thursday)
room 1.01, Pasteura 5 at 12:15
Wojciech Wiślicki (NCBJ)ODWOŁANE/CANCELLED: Results from LHCb and search for new physics
I am going to review experimental results on decays of heavy flavours b and c at high energy, as measured by the LHCb at CERN. The discussion will be focused on exclusive hadronic and semi-leptonic decays that may give interesting insights into CP violation and flavour anomalies. Estimates of uncertainties in the Standard Model predictions for such processes are under debate.
2020-03-05 (Thursday)
room 1.01, Pasteura 5 at 12:15
Michał Iglicki (IFT UW)Dark matter spin effects at future electron-positron colliders
Among great projects for the nearest decades, several new electron-positron colliders (e.g. ILC, CEPC, FCC-ee) are planned (or, at least, proposed) to be built. Basing on three simple (but QFT-consistent and renormalizable) models of spin-0, 1 and 1/2 dark matter, I will discuss whether DM could be produced and observed using the aforementioned machines operating near E_CM = 250 GeV, taking into account their predicted sensitivity and current experimental constraints. I will also indicate regions of the parameter space in which it could be easy to determine the spin of observed DM particle.
2020-02-27 (Thursday)
room 1.01, Pasteura 5 at 12:15
George Zoupanos (National Technical University, Athens, Greece)Reduction of Couplings and its application in a Finite Unified Theory and the MSSM
The method of reduction of couplings is applied to a Finite Unified Theory and in the MSSM. The method is based on searching for renormalization group invariant relations among couplings of a renormalizable theory which holds to all orders in perturbation theory. It leads to relations, at the unification scale, among gauge and Yukawa couplings (in the dimensionless sectors of the theory) and relations among the couplings of the trilinear terms and the Yukawa couplings, as well as a sum rule among the scalar masses and the gaugino mass (in the soft breaking sector). In the Finite Unified Theory model we predict, with remarkable agreement with the experiment, the masses of the top, bottom quarks and Higgs boson, while our predictions for the other Higgs masses and the supersymmetric spectrum are in comfortable agreement with the LHC bounds on the other Higgs and supersymmetric particles. Similar results are obtained in the case of reducing the MSSM.
2020-01-23 (Thursday)
room 1.01, Pasteura 5 at 12:15
Piotr Salabura (UJ)Studying QCD matter with virtual photons
Real and virtual photons decaying into dilepton pairs are unique probes to study microscopic properties of QCD matter produced in energetic heavy ion reactions. As they do not undergo the strong interaction and thus their mean free path is much longer than the size of hot and dense fireball created in such collisions, they carry out undisturbed information about temperature of the early phase of reaction and microscopic properties of its constituents. The latter ones are strongly connected to properties of light vector mesons acting as interpolating field between hadrons and photons.
In experiment, radiation of such pairs can be identified as the excess in the invariant mass of spectrum of dilepton pairs above the “cocktail” of known hadronic decays at the freeze-out of reaction. Such excess have been observed in various experiments from low energy SIS18 (√s ∼ 2 GeV) to top RHIC energies (√s ∼ 200 GeV) and recently also at LHC. The observed distributions are consistently described by a thermal-like emission from the fireball with an average temperature higher than the one concluded from hadron spectra. The distributions indicate strong melting of rho meson in hot and dense matter, the effect which is discussed in context of chiral symmetry restoration. In the talk review of experimental results and interpretations on aforementioned aspects will be given with special focus on recent results of the HADES experiment [1].
[1] Nature Phys. 15 (2019) no.10, 1040-1045]
In experiment, radiation of such pairs can be identified as the excess in the invariant mass of spectrum of dilepton pairs above the “cocktail” of known hadronic decays at the freeze-out of reaction. Such excess have been observed in various experiments from low energy SIS18 (√s ∼ 2 GeV) to top RHIC energies (√s ∼ 200 GeV) and recently also at LHC. The observed distributions are consistently described by a thermal-like emission from the fireball with an average temperature higher than the one concluded from hadron spectra. The distributions indicate strong melting of rho meson in hot and dense matter, the effect which is discussed in context of chiral symmetry restoration. In the talk review of experimental results and interpretations on aforementioned aspects will be given with special focus on recent results of the HADES experiment [1].
[1] Nature Phys. 15 (2019) no.10, 1040-1045]
2020-01-16 (Thursday)
room 1.01, Pasteura 5 at 12:15
Anna Socha (IFT UW)Truly dark vector dark matter
Motivated by the fact that so far all evidence for dark matter (DM) has a gravitational origin, I will explore an extreme possibility of the dark sector coupled to the Standard Model (SM) only through gravity. I will focus on the case where DM consists of spin-1 particles and investigate non-perturbative and several perturbative production mechanisms. In the first case, I will discuss particle creation in the time-varying gravitational background during the de Sitter stage of in ation. The latter will refer to the particle production during the reheating phase via the freeze-in from the SM particles' annihilation or as a result of the direct in aton decay. I will demonstrate that in each case there exists a viable range in parameter space that reproduces the observed relic abundance.
2020-01-09 (Thursday)
room 1.01, Pasteura 5 at 12:15
Aqeel Ahmed (Vrije University Brussel)A minimal model of neutral naturalness and dark matter
We propose a neutral naturalness model based on SO(7) × SU(7) symmetry, where SU(7) ⊃ SU(3)_c x SU(3)_{\hat{c}} × U(1)_X includes the SM color group SU(3)_{c} as well as a hidden sector color group SU(3)_{\hat{c}}. The global symmetry SO(7) is spontaneously broken at scale f to SO(6) resulting in 6 Goldstone bosons including the SM Higgs doublet H and a complex scalar χ charged under SU(2)_L ⊂ SO(6) and U(1)_D ⊂ SO(6), respectively. The top-partners in our model are SM color neutral, therefore they can be lighter than a TeV and still evade all the experimental constraints. However, these top partners are electroweak charged as a result they lead to interesting signatures at the LHC. The complex scalar χ serves as a dark matter candidate where its stability is ensured by the unbroken U(1)_D symmetry and is naturally light due to the psuedo-Goldstone nature. The dark matter χ in the mass range 100-500 GeV results in correct relic abundance and satisfies the direct and indirect constraints.
2019-12-19 (Thursday)
room 1.01, Pasteura 5 at 12:15
Aoife Bharucha (Marseille, CPT & Universite de Toulon)(Semi)Leptonic B and D decays: the latest news
An important influence on the field of heavy flavour physics in the last 6-7 years has been the appearance of several anomalies in measurements by LHCb and the B factories. These anomalies have affected both neutral and charged semi-leptonic B decays, and particularly in lepton flavour universality ratios, i.e. ratios of branching ratios with different flavoured leptons in the final state. I will review these anomalies, detailing the calculation of the observables and explain how the situation has evolved as a result of measurements presented at Moriond. I will further discuss the implications of these results for models beyond the Standard Model (BSM). Finally I will mention other measurements which could further test such BSM physics.
2019-12-12 (Thursday)
room 1.01, Pasteura 5 at 12:15
Stanisław Jadach (IFJ PAN, Kraków)Higher order QED corrections and soft photon resummation at FCC-ee
Major effort is needed to improve SM/QED predictions for FCC-ee observables by factor 10-200. In particular QED corrections for asymmetries near Z have to be improved by factor up to 200. New algorithms of extracting EW pseudo-observables from experimental data have to be worked out and cross-checked. Increased role of MC event generators is anticipated.
2019-12-05 (Thursday)
room 1.01, Pasteura 5 at 12:15
Mauro Napsuciale Mendívil (Universidad de Guanajuato, Mexico)Dark matter with a (1,0)+(0,1) space-time structure
In this talk we review our work on a new proposal for the space-time structure of dark matter. After a brief account of the algebraic structure and quantum field theory for fields with a (1,0)+(0,1) space-time structure described in a Dirac-like spinor language, we focus on the predictions of dark matter with this space-time structure for several observables in an effective field theory approach, and comparison with data including dark matter relic density, direct detection of dark matter (XENON1T results), indirect detection of dark matter (annihilation into standard model particles) and the gamma ray excess from the galactic center, which yields the sharp prediction M=M_{H}/2 for dark matter.