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Constraining dark matter particle properties with Fermi-LAT and the Cherenkov Telescope Array
Christopher Eckner, 2020, doctoral dissertation

Found in: ključnih besedah
Summary of found: ...dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric...
Keywords: dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric Cherenkov Telescope, Cherenkov Telescope Array, Fermi Large Area Telescope
Published: 29.09.2020; Views: 2497; Downloads: 92
.pdf Fulltext (68,77 MB)

Studying TDEs in the era of LSST
Katja Bricman, A. Gomboc, 2019, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...CA16104 Gravitational waves, black holes and fundamental physics (GWverse), supported by COST (European Cooperation in...
Keywords: The observing strategy with continuous scanning and large sky coverage of the upcoming ground-based Large Synoptic Survey Telescope (LSST) will make it a perfect tool in search of rare transients, such as Tidal Disruption Events (TDEs). Bright optical flares resulting from tidal disruption of stars by their host supermassive black hole (SMBH) can provide us with important information about the mass of the SMBH involved in the disruption and thus enable the study of quiescent SMBHs, which represent a large majority of SMBHs found in centres of galaxies. These types of transients are extremely rare, with only about few tens of candidates discovered so far. It is expected that the LSST will provide a large sample of new TDE light curves. Here we present simulations of TDE observations using an end-to-end LSST simulation framework. Based on the analysis of simulated light curves we estimate the number of TDEs with good quality light curves the LSST is expected to discover in 10 years of observations. In addition, we investigate whether TDEs observed by the LSST could be used to probe the SMBH mass distribution in the universe. The participation at this conference is supported by the Action CA16104 Gravitational waves, black holes and fundamental physics (GWverse), supported by COST (European Cooperation in Science and Technology).
Published: 04.01.2021; Views: 1713; Downloads: 0

Characterization of ambient aerosols in Mexico City during the MCMA-2003 campaign with aerosol mass spectrometry
Dara Salcedo, T. B. Onasch, Katja Džepina, M. R. Canagaratna, Qi Zhang, J. A. Huffman, P. F. DeCarlo, J. Jayne, P. Mortimer, D. Worsnop, 2006, original scientific article

Abstract: An Aerodyne Aerosol Mass Spectrometer (AMS) was deployed at the CENICA Supersite, during the Mexico City Metropolitan Area field study (MCMA-2003) from 31 March-4 May 2003 to investigate particle concentrations, sources, and processes. The AMS provides real time information on mass concentration and composition of the non-refractory species in particulate matter less than 1 mu m (NR-PM1) with high time and size-resolution. In order to account for the refractory material in the aerosol, we also present estimates of Black Carbon (BC) using an aethalometer and an estimate of the aerosol soil component obtained from Proton-Induced X-ray Emission Spectrometry (PIXE) analysis of impactor substrates. Comparisons of AMS + BC + soil mass concentration with other collocated particle instruments (a LASAIR Optical Particle Counter, a PM2.5 Tapered Element Oscillating Microbalance (TEOM), and a PM2.5 DustTrak Aerosol Monitor) show that the AMS + BC + soil mass concentration is consistent with the total PM2.5 mass concentration during MCMA-2003 within the combined uncertainties. In Mexico City, the organic fraction of the estimated PM2.5 at CENICA represents, on average, 54.6% (standard deviation sigma=10%) of the mass, with the rest consisting of inorganic compounds ( mainly ammonium nitrate and sulfate/ammonium salts), BC, and soil. Inorganic compounds represent 27.5% of PM2.5 (sigma=10%); BC mass concentration is about 11% (sigma=4%); while soil represents about 6.9% (sigma=4%). Size distributions are presented for the AMS species; they show an accumulation mode that contains mainly oxygenated organic and secondary inorganic compounds. The organic size distributions also contain a small organic particle mode that is likely indicative of fresh traffic emissions; small particle modes exist for the inorganic species as well. Evidence suggests that the organic and inorganic species are not always internally mixed, especially in the small modes. The aerosol seems to be neutralized most of the time; however, there were some periods when there was not enough ammonium to completely neutralize the nitrate, chloride and sulfate present. The diurnal cycle and size distributions of nitrate suggest local photochemical production. On the other hand, sulfate appears to be produced on a regional scale. There are indications of new particle formation and growth events when concentrations of SO2 were high. Although the sources of chloride are not clear, this species seems to condense as ammonium chloride early in the morning and to evaporate as the temperature increases and RH decreases. The total and speciated mass concentrations and diurnal cycles measured during MCMA-2003 are similar to measurements during a previous field campaign at a nearby location.
Found in: ključnih besedah
Keywords: aerosol mass-spectrometer, atmospheric aerosol, atmospheric chemistry, atmospheric physics
Published: 12.04.2021; Views: 1246; Downloads: 0
.pdf Fulltext (2,53 MB)

2009, other performed works

Abstract: recenzent 2021-
Found in: ključnih besedah
Summary of found: ... physics, chemistry, biology, mathematics, computer science, engineering...
Keywords: physics, chemistry, biology, mathematics, computer science, engineering
Published: 15.04.2021; Views: 1213; Downloads: 53
.docx Fulltext (266,05 KB)
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Application of machine learning techniques for cosmic ray event classification and implementation of a real-time ultra-high energy photon search with the surface detector of the Pierre Auger Observatory
Lukas Zehrer, 2021, doctoral dissertation

Abstract: Despite their discovery already more than a century ago, Cosmic Rays (CRs) still did not divulge all their properties yet. Theories about the origin of ultra-high energy (UHE, > 10^18 eV) CRs predict accompanying primary photons. The existence of UHE photons can be investigated with the world’s largest ground-based experiment for detection of CR-induced extensive air showers (EAS), the Pierre Auger Observatory, which offers an unprecedented exposure to rare UHE cosmic particles. The discovery of photons in the UHE regime would open a new observational window to the Universe, improve our understanding of the origin of CRs, and potentially uncloak new physics beyond the standard model. The novelty of the presented work is the development of a "real-time" photon candidate event stream to a global network of observatories, the Astrophysical Multimessenger Observatory Network (AMON). The stream classifies CR events observed by the Auger surface detector (SD) array as regards their probability to be photon nominees, by feeding to advanced machine learning (ML) methods observational air shower parameters of individual CR events combined in a multivariate analysis (MVA). The described straightforward classification procedure further increases the Pierre Auger Observatory’s endeavour to contribute to the global effort of multi-messenger (MM) studies of the highest energy astrophysical phenomena, by supplying AMON partner observatories the possibility to follow-up detected UHE events, live or in their archival data.
Found in: ključnih besedah
Summary of found: ...origin of CRs, and potentially uncloak new physics beyond the standard model. The novelty of the...
Keywords: astroparticle physics, ultra-high energy cosmic rays, ultra-high energy photons, extensive air showers, Pierre Auger Observatory, multi-messenger, AMON, machine learning, multivariate analysis, dissertations
Published: 27.10.2021; Views: 1741; Downloads: 119
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Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches
Piero Ullio, Mihael Petač, 2019, original scientific article

Abstract: We address the problem of reconstructing the phase-space 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 one-to-one 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 Lynden-Bell 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 phase-space 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 self-consistently defined corotating halo.
Found in: ključnih besedah
Summary of found: ...dark matter, astro physics of galaxies, high energy physics, phenomenology...
Keywords: dark matter, astrophysics of galaxies, high energy physics, phenomenology
Published: 01.10.2021; Views: 1044; Downloads: 0
.pdf Fulltext (1,22 MB)

Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations
Emmanuel Nezri, Julien Lavalle, Arturo Núñez-Castiñeyra, Mihael Petač, 2021, original scientific article

Abstract: Signal predictions for galactic dark matter (DM) searches often rely on assumptions regarding the DM phase-space distribution function (DF) in halos. This applies to both particle (e.g. p-wave suppressed or Sommerfeld-enhanced 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 steady-state collisionless Boltzmann equation (e.g. Eddington-like inversions, action-angle 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 zoomed-in hydrodynamical cosmological simulations in which one can access the true (coarse-grained) phase-space 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 10-20% level for velocity-dependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results.
Found in: ključnih besedah
Summary of found: ...matter simulations, dark matter theory, cosmology, nongalactic astro physics, astrophysics of galaxies, high energy physics...
Keywords: galaxy dynamics, dark matter experiments, dark matter simulations, dark matter theory, cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics
Published: 01.10.2021; Views: 1050; Downloads: 51
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Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect dark matter searches
Mihael Petač, 2020, original scientific article

Abstract: We for the first time provide self-consistent axisymmetric phase-space 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⊙≈10-2 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 DarkSide-20k 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 DM-induced 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 velocity-dependent annihilations. However, we find that accurate predictions are still hindered by large uncertainties regarding the DM distribution near the galactic center.
Found in: ključnih besedah
Summary of found: ...dark matter, astro physics, galaxies, high energy physics, experiments, phenomenology...
Keywords: dark matter, astrophysics, galaxies, high energy physics, experiments, phenomenology
Published: 01.10.2021; Views: 943; Downloads: 33
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Experimental bounds on sterile-active neutrino mixing angles
Mihael Petač, 2015, master's thesis

Abstract: 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 active-sterile 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.
Found in: ključnih besedah
Summary of found: ...Sterile neutrinos, Neutrino mixing, See-saw, High-Energy Physics - Phenomenology, High-Energy Physics - Experiments...
Keywords: Sterile neutrinos, Neutrino mixing, See-saw, High-Energy Physics - Phenomenology, High-Energy Physics - Experiments
Published: 01.10.2021; Views: 952; Downloads: 37
.pdf Fulltext (1,93 MB)

Testing effects of Lorentz invariance violation in the propagation of astroparticles with the Pierre Auger Observatory
Marko Zavrtanik, Danilo Zavrtanik, Serguei Vorobiov, Samo Stanič, Jon Paul Lundquist, Andrej Filipčič, P. Abreu, Lukas Zehrer, 2022, original scientific article

Found in: ključnih besedah
Summary of found: ...ray experiments, ultra high energy, cosmic rays, physics of the early universe, Pierre Auger Observatory,...
Keywords: cosmic ray experiments, ultra high energy, cosmic rays, physics of the early universe, Pierre Auger Observatory, Lorentz invariance violation effects
Published: 18.01.2022; Views: 814; Downloads: 29
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