Faculty of Physics University of Warsaw > Events > Seminars > "Theory of Particle Physics and Cosmology" Seminar

"Theory of Particle Physics and Cosmology" Seminar

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room 1.01, Pasteura 5 at 12:15

Carlos Tamarit (Technical University of Munich)

Revealing the Cosmic History with Gravitational Waves

The characteristics of the cosmic microwave background provide circumstantial evidence that the hot radiation-dominated epoch in the early universe was preceded by a period of inflationary expansion. Here, it will be shown how a measurement of the stochastic gravitational wave background can reveal the cosmic history and the physical conditions during inflation, subsequent pre- and reheating, and the beginning of the hot big bang era. This will be exemplified with a particularly well-motivated and predictive minimal extension of the Standard Model which is known to provide a complete model for particle physics -- up to the Planck scale, and for cosmology -- back to inflation.

room 1.01, Pasteura 5 at 12:15

Fotis Koutroulis (IFT UW)

A Profile of a Higgs mechanism under a UV and quantum, 1st order phase transition

We construct the zero temperature (no compact dimensions) effective action for an SU(2) Yang-Mills theory in five dimensions, with boundary conditions that reduce the symmetry on the four-dimensional boundary located at the origin to a U(1)-complex scalar system. In order to be sensitive to the Higgs phase, we need to include higher dimensional operators in the effective action, which can be naturally achieved by generating it by expanding the corresponding lattice construction in small lattice spacing, taking the naive continuum limit and then renormalizing. In addition, we build in the effective action non-perturbative information, related to a first order quantum phase transition known to exist. As a result, the effective action acquires a finite cut-off that is low and the fine tuning of the scalar mass is rather mild.

room 1.01, Pasteura 5 at 12:15

Rafał Masełek (IFT UW)

Supersymmetric muon g-2 with/without stable neutralino

We investigate a possibility to explain the discrepancy between the Standard Model predictions and the observed value of the anomalous magnetic moment of the muon within unorthodox SUSY scenarios in which neutralinos are unstable. We start by reviewing the muon g-2 calculations in the MSSM and confront it with the most up-to-date experimental constraints. We find out that the next generation of direct detection DM experiments combined with the current LHC results will ultimately test the parameter region that can explain the (g − 2)μ anomaly in the MSSM. Next, we study R-parity violating and gauge-mediated SUSY-breaking scenarios with unstable neutralinos. These models do not provide a viable DM candidate, which allows them to evade the DM constraints. We find that in RPV and GMSB with slepton NLSP the LHC constraints are weaker, and a large region of parameter space can explain the observed anomaly and evade experimental limits.

room 1.01, Pasteura 5 at 12:15

Dibyakrupa Sahoo (IFT UW)

Exploring new avenues to distinguish Dirac and Majorana neutrinos

Neutrinos are the only elementary fermions which might be their own antiparticles, i.e. they could be Majorana fermions. When a Majorana neutrino is exchanged in a process, it is possible to have lepton number violation. This has been used to propose various probes for Majorana neutrinos, such as the neutrinoless double beta decay. Additionally, if a Majorana neutrino is quantum mechanically indistinguishable from its antiparticle, quantum statistical considerations could as well be exploited. Since neutrino and antineutrino are never detected close to their point of production, formulating such quantum statistical probes have always been challenging. In this talk we will present a few ideas that exploit quantum statistics to probe Majorana neutrinos. These probes are interesting because they are not necessarily constrained by the smallness of neutrino mass. Such probes can potentially probe whether neutrinos participate in any non-standard interactions as well.

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Toshinori Matsui (KIAS, Seul)

Flavor dependent U(1) symmetric Zee model

We have extended the Zee model by introducing a vector-like lepton doublet with a flavor-dependent global U(1) symmetry. Due to the U(1) symmetry, flavor-changing neutral currents in the quark sector can be naturally forbidden at tree level, while a sufficient amount of lepton flavor violation allows satisfying current neutrino oscillation data. In our model, additional sources of CP-violation appear in the lepton sector, but their contribution to electric dipole moments is much smaller than current experimental bounds due to the Yukawa structure constrained by the U(1) symmetry. We have found that there is a parameter region where the strongly first order EW phase transition can be realized, which is necessary for the successful scenario of the EW baryogenesis in addition to new CP-violating phases. Finally, the detail of collider phenomenology is discussed.
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room 1.01, Pasteura 5 at 12:15

Keisuke Harigaya (CERN)

Cosmology of Axion Rotation

We will introduce new cosmological dynamics of the QCD axion and axion-like particles, where the axion field rotates in field space. Axion dark matter may be produced from the kinetic energy of the axion and the required axion decay constant is much below the prediction of the conventional evolutions. The angular momentum of the rotation is transferred into baryon asymmetry through baryon number violating interactions. We discuss the electroweak sphaleron process, Majorana neutrino mass, and R-parity violation and predictions on the parameters of each theory. In some of the parameter space the rotation dominates the energy density of the universe. The resultant kination-dominated era modifies primordial gravitational wave spectra.

room 1.01, Pasteura 5 at 12:15

Bernat Capdevila (Turin University and INFN Turin)

Inclusive semileptonic B-meson decays and CKM matrix determinations: challenges and theoretical framework(s)

The CKM matrix is a key ingredient in the study of CP violation and in New Physics searches within the flavour sector. Therefore, precise determinations of its matrix elements are of utmost importance. |Vub| and |Vcb| can be extracted from both exclusive semileptonic b —> u and b —> c decays and the inclusive channels B —> Xu l nu and B —> Xc l nu. Exclusive and inclusive determinations of these matrix elements have been in tension for a long time, with even different theoretical frameworks not agreeing well with one another. In this seminar, I am going to review some of the techniques employed in the study of inclusive semileptonic B-meson decays and present the results of our latest inclusive determination of |Vcb|. Then, I will discuss the challenges one needs to face in order to obtain a solid description for B —> Xu l nu and some of the solutions proposed. Finally, I will present the first calculation of power-suppressed perturbative corrections in B —> Xu l nu and show the first preliminary results of our determination of the necessary non-perturbative functions within a neural network approach.

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Kai Schmitz (CERN)

Big Bang Chemistry and the Baryon Asymmetry of the Universe

The chemical equilibrium in the early Universe dynamically evolves in dependence of the steadily decreasing temperature of the Standard Model plasma. At high temperatures, when the rate of many Standard Model interactions cannot compete with the fast expansion rate, the chemical transport in the plasma is in particular characterized by a large number of global charges that only become violated at lower temperatures. This observation leads to a new perspective on the necessary conditions for the successful generation of the baryon asymmetry of the Universe (BAU). As I will show in this talk, it turns out that the BAU cannot only be generated in "baryogenesis" or "baryogenesis via leptogenesis", but also in "baryogenesis via leptogenesis via chargegenesis", which starts out from the generation of one or several of the many global charges that are available at high temperatures. This new scenario significantly relaxes the Sakharov conditions and opens up a new window to a plethora of model-building opportunities. As an example of "chargegenesis", I will consider axion inflation, which can give rise to global charges at high temperatures that are subsequently converted by right-handed-neutrino interactions to a new B-L-violating chemical equilibrium at low temperatures. In the last part of the talk, I will discuss how this new mechanism of B-L violation ("wash-in leptogenesis", see 2011.09347) can be generalized to the generation of flavored B-L charges, even if the total B-L charge remains zero in all sectors and at all times ("wash-in leptoflavorgenesis", see 2111.03082). In both cases, weak sphaleron processes are then responsible for the final conversion from (flavored) baryon-minus-lepton number to baryon number.
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room 1.01, Pasteura 5 at 12:15

Iñaki Lara Pérez (IFT UW)

New constraints over the μνSSM from long-lived particle searches at the LHC

The μνSSM is the minimal supersymmetric extension of the standard model capable of solving the mu problem of the MSSM and generating neutrino masses, through an R-parity violating coupling between Higgs superfields and righ-handed neutrino superfields.The smallness of the neutrino Yukawa coupling, necessary for generating correct neutrino physics, dictates the size of the R-parity violating (RPV) interactions. We analyze the implications for the model of the last published MUON G-2 result, as well as the LHC constraints over the top superpartner as the LSP of the model.

join us at 12:15

Roberto Vega-Morales (Granada University)

Dark Matter Schwinger Production

Building on recently introduced inflationary vector dark matter production mechanisms as well as electromagnetic Schwinger production mechanisms which take place during inflation, we show that an inflationary dark Schwinger mechanism can generate the observed dark matter relic abundance. This dark Schwinger mechanism can lead to a multi-component dark matter sector which is comprised of some mixture of dark vectors, dark charged scalars and, in principle, dark fermions that interact amongst themselves.
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