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 1 - 10 / 1712 1.Prospects On Testing Lorentz Invariance Violation With The Cherenkov Telescope ArrayMarko Zavrtanik, Danilo Zavrtanik, Gabrijela Zaharijas, Lili Yang, Serguei Vorobiov, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, M. K. Daniel, 2015, published scientific conference contributionFound in: ključnih besedahSummary of found: ...Cherenkov Telescope Array (CTA), Lorentz Invariance Violation (LIV), Very High Energy (VHE) gamma-rays, fundamental physics probes, Active Galactic Nuclei...Keywords: Cherenkov Telescope Array (CTA), Lorentz Invariance Violation (LIV), Very High Energy (VHE) gamma-rays, fundamental physics probes, Active Galactic Nuclei (AGN), Gamma Ray Bursts (GRBs), pulsarsPublished: 14.03.2016; Views: 3305; Downloads: 190 Fulltext (904,49 KB) 2.Indirect Detection ExperimentsGabrijela Zaharijas, 2017, published scientific conference contribution abstract (invited lecture)Found in: ključnih besedahSummary of found: ...a significant number of experiments actively monitoring high-energy Universe. Many of these probes provide excellent... ...live in a golden age for astro-particle physics, with a significant number of experiments actively...Keywords: We live in a golden age for astro-particle physics, with a significant number of experiments actively monitoring high-energy Universe. Many of these probes provide excellent tests of particle physics models of dark matter particles. In particular, experiments such as Fermi -LAT, AMS-02, Ice Cube, ... are significantly cutting into the parameter space of one of the most popular candidates, the WIMPs. In this talk I will describe some of the strategies and methods used to search for dark matter with astrophysical data. Special attention will be given to the latest indications of an unaccounted gamma-ray excess at few GeV in the Fermi-LAT data in the region around the Galactic Centre, which steered lots of attention as it was shown to be consistent with putative signals of WIMP dark matter particles and complementary constraints provided by other experiments. Finally I will discuss projections of the expected sensitivities with upcoming experiments and continued data taking with current ones.Published: 17.07.2017; Views: 3495; Downloads: 0 Fulltext (50,35 MB) 3.Multi-Messenger Physics With the Pierre Auger ObservatoryKarl-Heinz Kampert, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, original scientific articleFound in: ključnih besedahSummary of found: ...Pierre Auger Observatory, ultra- high energy cosmic rays, photons, neutrinos, protons, multi-messenger...Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, photons, neutrinos, protons, multi-messenger physics and astrophysicsPublished: 06.05.2019; Views: 2016; Downloads: 83 Fulltext (2,46 MB) 4.Mass composition of ultra-high energy cosmic rays at the Pierre Auger ObservatoryGašper Kukec Mezek, 2019, doctoral dissertationAbstract: Cosmic rays with energies above 10^18 eV, usually referred to as ultra-high energy cosmic rays (UHECR), have been a mystery from the moment they have been discovered. Although we have now more information on their extragalactic origin, their direct sources still remain hidden due to deviations caused by galactic magnetic fields. Another mystery, apart from their production sites, is their nature. Their mass composition, still uncertain at these energies, would give us a better understanding on their production, acceleration, propagation and capacity to produce extensive air showers in the Earth's atmosphere. Mass composition studies of UHECR try to determine their nature from the difference in development of their extensive air showers. In this work, observational parameters from the hybrid detection system of the Pierre Auger Observatory are used in a multivariate analysis to obtain the mass composition of UHECR. The multivariate analysis (MVA) approach combines a number of mass composition sensitive variables and tries to improve the separation between different UHECR particle masses. Simulated distributions of different primary particles are fitted to measured observable distributions in order to determine individual elemental fractions of the composition. When including observables from the surface detector, we find a discrepancy in the estimated mass composition between a mixed simulation sample and the Pierre Auger data. Our analysis results from the Pierre Auger data are to a great degree independent on hadronic interaction models. Although they differ at higher primary masses, the different models are more consistent, when combining fractions of oxygen and iron. Compared to previously published results, the systematic uncertainty from hadronic interaction models is roughly four times smaller. Our analysis reports a predominantly heavy composition of UHECR, with more than a 50% fraction of oxygen and iron at low energies. The composition is then becoming heavier with increasing energy, with a fraction of oxygen and iron above 80% at the highest energies.Found in: ključnih besedahSummary of found: ...astroparticle physics, ultra-high energy cosmic rays, extensive air showers,...Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, machine learning, multivariate analysisPublished: 03.04.2019; Views: 2968; Downloads: 136 Fulltext (17,53 MB) 5.Mass composition of cosmic rays with energies from 10^17.2 eV to 10^20 eV using surface and fluorescence detectors of the Pierre Auger ObservatoryGašper Kukec Mezek, 2018, published scientific conference contributionAbstract: Ultra-high-energy cosmic rays (UHECRs) are highly energetic particles with EeV energies, exceeding the capabilities of man-made colliders. They hold information on extreme astrophysical processes that create them and the medium they traverse on their way towards Earth. However, their mass composition at such energies is still unclear, because data interpretation depends on our choice of high energy hadronic interaction models. With its hybrid detection method, the Pierre Auger Observatory has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations (SD) and fluorescence telescopes (FD). We present recent mass composition results from the Pierre Auger Collaboration using observational parameters from SD and FD measurements. Using the full dataset of the Pierre Auger Observatory, implications on composition can be made for energies above 10^17.2 eV.Found in: ključnih besedahSummary of found: ...Ultra- high-energy cosmic rays (UHECRs) are highly energetic particles... ...astroparticle physics, ultra-high energy cosmic rays, extensive air showers,...Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stationsPublished: 24.05.2019; Views: 2130; Downloads: 82 Fulltext (573,00 KB) 6.Measurement of the proton-air cross section with Telescope Array’s Middle Drum detector and surface array in hybrid modeJ. P. Lundquist, R.U. Abbasi, 2015, original scientific articleFound in: ključnih besedahSummary of found: ...Cosmic Rays, proton cross-section, ultra- high energy, particle physics...Keywords: Cosmic Rays, proton cross-section, ultra-high energy, particle physicsPublished: 27.04.2020; Views: 1580; Downloads: 0 Fulltext (409,81 KB) 7.Energy response of ISS-CREAM calorimeter with attenuation effectJ. P. Lundquist, H.G. Zhang, 2020, other component partsAbstract: The NASA mission, Cosmic Ray Energetic And Mass experiment for the International Space Station (ISS-CREAM) is to measure individual cosmic-ray particle energy spectra from protons to iron nuclei, with an energy range from ~1 TeV to the so-called "knee", near 1015eV. Energies of cosmic-ray particles are measured from electromagnetic showers induced by particles in the calorimeter. As a pioneer mission, the balloon-borne CREAM instrument has successfully flown seven times over the Antarctica for a cumulative exposure of 191 days. The CREAM calorimeter has shown sufficient capability to measure energies of cosmic-ray particles by capturing the electromagnetic shower profile within the interested energy range. The ISS-CREAM calorimeter is expected to have a similar performance and, before it was launched, an engineering-unit calorimeter was shipped to CERN for a full beam test. The full performance test includes position, energy, and angle scans of electron and pion beams together with a high voltage scan for calibration and characterization. In addition to the regular analysis for performance test, we also applied an additional step to generate the universal energy responses by correcting the attenuation effect in the calorimeter readout. The general energy responses could be obtained after shifting the incident beam positions to a reference position near the center of the calorimeter, which provided improved energy resolutions. The result of this analysis will be used to determine the incident energies of the cosmic-ray particles in the flight data.Found in: ključnih besedahSummary of found: ...electron and pion beams together with a high voltage scan for calibration and characterization. In addition... ...cosmic rays, high-energy, particle physics, detectors...Keywords: cosmic rays, high-energy, particle physics, detectorsPublished: 29.04.2020; Views: 1648; Downloads: 80 Fulltext (2,54 MB) 8.On the GeV Emission of the Type I BdHN GRB 130427ALaura Beccera, She Sheng Xue, Yu Wang, Narek Sahakyan, Mile Karlica, Yen-Chen Chen, Simonetta Filippi, Christian Cherubini, Carlo Luciano Bianco, Jorge Armando Rueda, Rahim Moradi, Remo Ruffini, 2019, original scientific articleAbstract: We propose that the inner engine of a type I binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field B_0 aligned with the BH rotation axis and surrounded by an ionized plasma of extremely low density of 10^−14 g cm−3. Using GRB 130427A as a prototype, we show that this inner engine acts in a sequence of elementary impulses. Electrons accelerate to ultrarelativistic energy near the BH horizon, propagating along the polar axis, θ = 0, where they can reach energies of ~10^18 eV, partially contributing to ultrahigh-energy cosmic rays. When propagating with $\theta \ne 0$ through the magnetic field B_0, they produce GeV and TeV radiation through synchroton emission. The mass of BH, M = 2.31M ⊙, its spin, α = 0.47, and the value of magnetic field B_0 = 3.48 × 10^10 G, are determined self consistently to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${ \mathcal E }\sim {10}^{37}$ erg is ~10^−14 s at the beginning of the process, then slowly increases with time evolution. In principle, this "inner engine" can operate in a gamma-ray burst (GRB) for thousands of years. By scaling the BH mass and the magnetic field, the same inner engine can describe active galactic nuclei.Found in: ključnih besedahSummary of found: ...gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical Phenomena... ...black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics...Keywords: black hole physics, binaries, gamma-ray burst, neutron stars, supernovae, Astrophysics - High Energy Astrophysical PhenomenaPublished: 20.07.2020; Views: 1510; Downloads: 0 Fulltext (1,09 MB) 9.Constraining dark matter particle properties with Fermi-LAT and the Cherenkov Telescope ArrayChristopher Eckner, 2020, doctoral dissertationFound in: ključnih besedahSummary of found: ...dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric Cherenkov...Keywords: dark matter, astroparticle physics, high-energy gamma-ray astronomy, cosmic rays, Imaging Atmospheric Cherenkov Telescope, Cherenkov Telescope Array, Fermi Large Area TelescopePublished: 29.09.2020; Views: 1864; Downloads: 57 Fulltext (68,77 MB) 10.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 ObservatoryLukas Zehrer, 2021, doctoral dissertationAbstract: 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 besedahSummary 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, dissertationsPublished: 27.10.2021; Views: 878; Downloads: 34 Fulltext (0,00 KB)This document has many files! More...
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