1. Experimental bounds on sterileactive neutrino mixing anglesMihael Petač, 2015, magistrsko delo Opis: Despite the success of the Standard Model in the last few decades, we know it is not complete. There is strong motivation for assuming the existence of additional heavy neutral leptons, which can account for active neutrino masses and possibly also have cosmological implications. In this work I consider the Standard Model with two neutral lepton singlets (sterile neutrinos) with degenerated masses in the range 20MeV  2GeV. The constraints on the activesterile neutrino mixing angles are evaluated based on recent neutrino oscillations data. Using these constraints the bounds from accelerator experiments are reanalyzed for the case of the considered model. Finally, the results are compared with cosmological constraints coming from Big Bang nucleosynthesis and the nMSM resonant leptogenesis. Najdeno v: osebi Ključne besede: Sterile neutrinos, Neutrino mixing, Seesaw, HighEnergy Physics  Phenomenology, HighEnergy Physics  Experiments Objavljeno: 01.10.2021; Ogledov: 809; Prenosov: 29 Polno besedilo (1,93 MB) 
2. On velocitydependent dark matter annihilations in dwarf satellitesMauro Valli, Piero Ullio, Mihael Petač, 2018, izvirni znanstveni članek Opis: Milky Way dwarf spheroidal satellites are a prime target for Dark Matter (DM) indirect searches. There have been recent reassessments of the expected DM gammaray signals in case of longrange interactions, commonly known as Sommerfeld enhancement. Since details of the underlying DM phasespace distribution function become critical, there are potentially large uncertainties in the final result. We provide here a first attempt towards a comprehensive investigation of these systematics, addressing the impact on the expected DM flux from Milky Way dwarfs via Bayesian inference on the available stellar kinematic datasets. After reconsidering the study case of ergodic systems, we investigate for the first time scenarios where DM particle orbits may have a radial or tangential bias. We consider both cuspy and cored parametric DM density profiles, together with the case of a nonparametric halo modelling directly connected to lineofsight observable quantities. The main findings of our work highlight the relevance of the assumed phasespace distribution: Referring to a generalized Jfactor, namely the lineofsight convolution of the spatial part in case of velocitydependent annihilation rate, an enhancement (suppression) with respect to the limit of isotropic phasespace distributions is obtained for the case of tangentially (radially) biased DM particle orbits. We provide new estimates for Jfactors for the eight brightest Milky Way dwarfs also in the limit of velocityindependent DM annihilation, in good agreement with previous results in literature, and derive datadriven lowerbounds based on the nonparametric modelling of the halo density. The outcome of our broad study stands out as a representative of the stateoftheart in the field, and falls within the interest of current and future experimental collaborations involved in DM indirect detection programs. Najdeno v: osebi Ključne besede: dark matter, indirect detection, dwarf satellites, sommerfeld enhancement, gammarays Objavljeno: 01.10.2021; Ogledov: 784; Prenosov: 27 (1 glas) Polno besedilo (0,00 KB) Gradivo ima več datotek! Več...

3. Twointegral distribution functions in axisymmetric galaxies: Implications for dark matter searchesPiero Ullio, Mihael Petač, 2019, izvirni znanstveni članek Opis: We address the problem of reconstructing the phasespace distribution function for an extended collisionless system, with known density profile and in equilibrium within an axisymmetric gravitational potential. Assuming that it depends on only two integrals of motion, namely the energy and the component of the angular momentum along the axis of symmetry Lz , there is a onetoone correspondence between the density profile and the component of the distribution function that is even in Lz, as well as between the weighted azimuthal velocity profile and the odd component. This inversion procedure was originally proposed by LyndenBell and later refined in its numerical implementation by Hunter and Qian; after overcoming a technical difficulty, we apply it here for the first time in presence of a strongly flattened component, as a novel approach of extracting the phasespace distribution function for dark matter particles in the halo of spiral galaxies. We compare results obtained for realistic axisymmetric models to those in the spherical symmetric limit as assumed in previous analyses, showing the rather severe shortcomings in the latter. We then apply the scheme to the Milky Way and discuss the implications for the direct dark matter searches. In particular, we reinterpret the null results of the Xenon1T experiment for spin(in)dependent interactions and make predictions for the annual modulation of the signal for a set of axisymmetric models, including a selfconsistently defined corotating halo. Najdeno v: osebi Ključne besede: dark matter, astrophysics of galaxies, high energy physics, phenomenology Objavljeno: 01.10.2021; Ogledov: 891; Prenosov: 0 Polno besedilo (1,22 MB) 
4. Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect dark matter searchesMihael Petač, 2020, izvirni znanstveni članek Opis: We for the first time provide selfconsistent axisymmetric phasespace distribution models for the Milky Way's dark matter (DM) halo which are carefully matched against the latest kinematic measurements through Bayesian analysis. By using broad priors on the individual galactic components, we derive conservative estimates for the astrophysical factors entering the interpretation of direct and indirect DM searches. While the resulting DM density profiles are in good agreement with previous studies, implying ρ⊙≈102 M⊙/pc3, the presence of baryonic disc leads to significant differences in the local DM velocity distribution in comparison with the standard halo model. For direct detection, this implies roughly 30% stronger cross section limits at DM masses near detectors maximum sensitivity and up to an order of magnitude weaker limits at the lower end of the mass range. Furthermore, by performing Monte Carlo simulations for the upcoming DARWIN and DarkSide20k experiments, we demonstrate that upon successful detection of heavy DM with coupling just below the current limits, the carefully constructed axisymmetric models can eliminate bias and reduce uncertainties by more then 50% in the reconstructed DM coupling and mass, but also help in a more reliable determination of the scattering operator. Furthermore, the velocity anisotropies induced by the baryonic disc can lead to significantly larger annual modulation amplitude and sizable differences in the directional distribution of the expected DMinduced events. For indirect searches, we provide the differential J factors and compute several moments of the relative velocity distribution that are needed for predicting the rate of velocitydependent annihilations. However, we find that accurate predictions are still hindered by large uncertainties regarding the DM distribution near the galactic center. Najdeno v: osebi Ključne besede: dark matter, astrophysics, galaxies, high energy physics, experiments, phenomenology Objavljeno: 01.10.2021; Ogledov: 818; Prenosov: 26 Polno besedilo (0,00 KB) Gradivo ima več datotek! Več...

5. Galactic dark matter distribution and its implications for experimental searchesMihael Petač, 2019, doktorska disertacija Najdeno v: osebi Ključne besede: dark matter, phasespace distribution function, dwarf spheroidal galaxies, spiral galaxies, Milky Way, dissertations, direct detection, indirect detection Objavljeno: 01.10.2021; Ogledov: 1002; Prenosov: 0 Polno besedilo (72,39 MB) 
6. Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulationsEmmanuel Nezri, Julien Lavalle, Arturo NúñezCastiñeyra, Mihael Petač, 2021, izvirni znanstveni članek Opis: Signal predictions for galactic dark matter (DM) searches often rely on assumptions regarding the DM phasespace distribution function (DF) in halos. This applies to both particle (e.g. pwave suppressed or Sommerfeldenhanced annihilation, scattering off atoms, etc.) and macroscopic DM candidates (e.g. microlensing of primordial black holes). As experiments and observations improve in precision, better assessing theoretical uncertainties becomes pressing in the prospect of deriving reliable constraints on DM candidates or trustworthy hints for detection. Most reliable predictions of DFs in halos are based on solving the steadystate collisionless Boltzmann equation (e.g. Eddingtonlike inversions, actionangle methods, etc.) consistently with observational constraints. One can do so starting from maximal symmetries and a minimal set of degrees of freedom, and then increasing complexity. Key issues are then whether adding complexity, which is computationally costy, improves predictions, and if so where to stop. Clues can be obtained by making predictions for zoomedin hydrodynamical cosmological simulations in which one can access the true (coarsegrained) phasespace information. Here, we test an axisymmetric extension of the Eddington inversion to predict the full DM DF from its density profile and the total gravitational potential of the system. This permits to go beyond spherical symmetry, and is a priori well suited for spiral galaxies. We show that axisymmetry does not necessarily improve over spherical symmetry because the (observationally unconstrained) angular momentum of the DM halo is not generically aligned with the baryonic one. Theoretical errors are similar to those of the Eddington inversion though, at the 1020% level for velocitydependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results. Najdeno v: osebi Ključne besede: galaxy dynamics, dark matter experiments, dark matter simulations, dark matter theory, cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics Objavljeno: 01.10.2021; Ogledov: 912; Prenosov: 42 Polno besedilo (0,00 KB) Gradivo ima več datotek! Več...
