Seminarium "Teoria cząstek elementarnych i kosmologia"
2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025
2023-03-23 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15 
Robert Ziegler (KIT Karlsruhe)Flavor Probes of Axion Dark Matter
Standard Model extensions with light axions are well-motivated by the observed Dark Matter abundance and the Peccei-Quinn solution to the Strong CP Problem. In general such axions can have large flavor-violating couplings to SM fermions, which naturally arise in scenarios where the Peccei-Quinn symmetry also explains the hierarchical pattern of fermion masses and mixings. After a pedagogical introduction, I will discuss how these couplings allow for efficient axion production from the decays of SM particles, giving the opportunity to probe axion Dark Matter with precision flavor experiments, astrophysics and cosmology.
2023-03-16 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Paola Delgado (UJ Kraków)Constraining the bispectrum from bouncing cosmologies with Planck
Bouncing models followed by an inflationary phase can not only generate almost scale invariant fluctuation spectra, but also mitigate the large-scale anomalies of the Cosmic Microwave Background (CMB) by considering large non-Gaussianities on very large scales, which decay exponentially inside the horizon. For this reason, this non-Gaussianity was thought to be invisble in observations, as they only probe sub-horizon scales. In this talk I explain how such models can be excluded with high signifcances by the Planck data if their non-Gaussianity is enough to appreciably alleviate the large-scale anomalies. This result also shows the sensitivity of the Planck data to scales beyond the pivot scale.
2023-03-09 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Toni Mäkelä (NCBJ Warsaw)Investigation of the scale dependence of the top quark mass in short-distance schemes
The mass of the top quark plays an important role in many predictions both within and beyond the standard model of particle physics. For instance, it is a central ingre- dient in the determination of the stability of the electroweak vacuum. However, quarks are never observed as free particles, and the pole mass defined as an analogue to a free particle’s mass suffers from an inherent theoretical ambiguity. This is avoided by using short-distance schemes, in which quark masses become renormalization scale de- pendent quantities. In the present work, the computation of the single-differential top quark-antiquark pair production cross section at next-to-leading order in the fixed-order expansion is examined consistently using the so-called MSR and modified minimal sub- traction schemes. A thorough investigation of the mass renormalization scale dependence of the pair invariant mass spectrum is carried out for the first time. The importance of a proper scale choice for obtaining robust cross-section predictions is discussed, and its effect on the extraction of the top quark mass from LHC data is demonstrated.
2023-03-02 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Marco Piva (IFT UW)Renormalizable and unitary theory of quantum gravity with purely virtual particles
Purely virtual particles, or fakeons, are degrees of freedom of a new type that mediate interactions but cannot appear as external on-shell states. The main application of fakeons is quantum gravity, which can be made both renormalizable and unitary. After discussing the nonrenormalizability of Einstein theory and the non-unitarity of higher-derivative gravity, I will show in detail how to endow quantum field theory with purely virtual particles. Then, I will present the main features of the theory of quantum gravity and show its predictions in inflationary cosmology. Finally, I will conclude with some remarks on fakeons in the context of particle physics.
2023-01-26 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Ville Vaskonen (NICPB, Tallinn)Formation of early galaxies and supermassive black holes
The JWST has recently detected surprisingly luminous early galaxies indicating a tension with the LCDM. In this talk, I will describe these observations and discuss different new physics scenarios that could explain them. In addition, I will discuss how the gravitational wave observations can cast light on the formation of supermassive black holes as well as early galaxies, and speculate on a possible connection between the JWST and pulsar timing array observations.
2023-01-16 (Poniedziałek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Kodai Sakurai (IFT UW)NLO corrections to heavy Higgs boson decays in 2HDM
The interactions of the discovered Higgs boson have been scrutinized in the LHC experiments. The current measurement results show that the properties of the discovered Higgs boson are consistent with the SM. This fact constrains wide parameter space in extended Higgs models. However, many models can fit with the current results by considering the near alignment scenario where the predictions of the Higgs boson couplings are SM-like. The intriguing thing in the near-alignment scenario is that behaviors of the heavy Higgs boson decays can be drastically changed, depending on the size of deviations in the Higgs boson couplings. This indicates that NLO corrections to the heavy Higgs boson decays can be significant in the near alignment scenario. In particular, this is the case for the decay processes that vanish in the alignment limit (e.g., A-->Zh, H-->hh). In this talk, taking two Higgs doublet models (2HDMs) as concrete examples, we show the impact of NLO corrections on the heavy Higgs boson decays. We also demonstrate that types of 2HDMs can be discriminated by the decay pattern of the CP-odd Higgs boson.
2023-01-12 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Marek Lewicki (IFT UW)Search for new physics through primordial gravitational wave signals
We are currently witnessing the dawn of a new era in astrophysics and cosmology, started by the LIGO/Virgo observations of Gravitational Waves (GW). Thanks to the fact that these signals propagate freely from the moment of their production they also open a new window into processes taking place in the first moments of our Universe. Before we had to rely on photon based signals which could only propagate freely since the Universe became transparent due to recombination when it was about 370k years old. I will discuss prospects for detection of a GW signal from the early Universe with the next generation of experiments. My focus will be sources associated with cosmological phase transitions. I will discuss recent updates on the modelling of these events and their impact on the resulting GW spectra.
2022-12-15 (Czwartek)
Zapraszamy na spotkanie o godzinie 12:15
Michał Czakon (RWTH Aachen)[ON-LINE] Standard Model theory for the LHC: the present and the future
This seminar will take place on-line only
Direct searches for New Physics at the Large Hadron Collider still remain unsuccessful. This has led to a paradigm shift towards indirect searches which rely on discrepancies between theory predictions and experimental measurements. Not long ago, experimental data was only compared to Monte Carlo simulations obtained with the help of parton-shower event generators, while precise theoretical predictions were only available for simplified process definitions far from the experimental reality. In consequence, the usefulness of the measurements was, and still is to a large extent, limited due to systematic uncertainties. In order to remedy this situation, there is an ongoing tremendous effort of the theory community towards a better understanding of Standard Model effects in a realistic setting. I will review the current leading edge results, in particular predictions for higher multiplicity final states, precise predictions for standard-candle processes, and the road towards improved modelling at fixed order perturbation theory. I will also mention progress beyond strict fixed order calculations.
2022-12-08 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Andrew Cheek (CAMK)Primordial Black Hole Evaporation: implications for dark matter and dark radiation
Hawking evaporation of black holes is expected to copiously produce all kinds of particles, regardless of their charges. For primordial black holes (PBHs) of a certain mass and abundance, the implications for the early Universe can be huge, they can lead to early matter domination, produce gravitational wave signals and can even aid baryogenesis. In this talk I will discuss how future measurements of the CMB will provide constraints on black hole distributions, but to a much lesser extent than previously thought. Then I will discuss how Hawking evaporation provides an efficient way of producing dark matter by way of gravity only. I will also discuss the interplay between PBH production and interacting dark matter. For these works I made use of the public code I co developed called FRISBHEE, which solves the system of coupled Friedmann-Boltzmann equations. This talk will be based on Phys.Rev.D 105 (2022) 1, 015022, Phys.Rev.D 105 (2022) 1, 015023 and Phys.Rev.D 106 (2022) 10, 103012, as well as ongoing works.
2022-12-01 (Czwartek)
Zapraszamy do sali 1.01, ul. Pasteura 5 o godzinie 12:15
Mateusz Czaja (IFT UW)Determination of V_cb from inclusive semileptonic B-meson decays
A precise determination of the Vcb element of the CKM matrix plays an important role in restricting uncertainties in several phenomenologically important observables. Its value can be extracted from the decay width and kinematic moments of the inclusive semileptonic decay of the B meson. In this talk, I will review the theoretical framework used in calculations of these quantities. I will focus on developments in the computation of the di-lepton mass squared q2 moments, and discuss their role in the extraction of Vcb, facilitated by recent experiments in Belle and Belle II. I will also discuss the ongoing computation of O(alpha_s^3) perturbative corrections to the full q2 spectrum.
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