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131.
Calibration of the underground muon detector of the Pierre Auger Observatory
A. Aab, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Marta Trini, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2021, izvirni znanstveni članek

Opis: To obtain direct measurements of the muon content of extensive air showers with energy above 10[sup]16.5 eV, the Pierre Auger Observatory is currently being equipped with an underground muon detector (UMD), consisting of 219 10 m[sup]2-modules, each segmented into 64 scintillators coupled to silicon photomultipliers (SiPMs). Direct access to the shower muon content allows for the study of both of the composition of primary cosmic rays and of high-energy hadronic interactions in the forward direction. As the muon density can vary between tens of muons per m[sup]2 close to the intersection of the shower axis with the ground to much less than one per m[sup]2 when far away, the necessary broad dynamic range is achieved by the simultaneous implementation of two acquisition modes in the read-out electronics: the binary mode, tuned to count single muons, and the ADC mode, suited to measure a high number of them. In this work, we present the end-to-end calibration of the muon detector modules: first, the SiPMs are calibrated by means of the binary channel, and then, the ADC channel is calibrated using atmospheric muons, detected in parallel to the shower data acquisition. The laboratory and field measurements performed to develop the implementation of the full calibration chain of both binary and ADC channels are presented and discussed. The calibration procedure is reliable to work with the high amount of channels in the UMD, which will be operated continuously, in changing environmental conditions, for several years.
Ključne besede: ultra-high energy cosmic rays, extensive air showers (EAS), EAS muonic component, Pierre Auger Observatory, underground muon detector, detector calibration
Objavljeno v RUNG: 14.04.2021; Ogledov: 2737; Prenosov: 139
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132.
Search for large-scale anisotropy on arrival directions of ultra-high-energy cosmic rays observed with the telescope array experiment
R. U. Abbasi, Mitsuhiro Abe, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, Douglas R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Motivated by the detection of a significant dipole structure in the arrival directions of ultra-high-energy cosmic rays above 8 EeV reported by the Pierre Auger Observatory (Auger), we search for a large-scale anisotropy using data collected with the surface detector array of the Telescope Array Experiment (TA). With 11 yr of TA data, a dipole structure in a projection of the R.A. is fitted with an amplitude of 3.3% ± 1.9% and a phase of 131° ± 33°. The corresponding 99% confidence-level upper limit on the amplitude is 7.3%. At the current level of statistics, the fitted result is compatible with both an isotropic distribution and the dipole structure reported by Auger.
Ključne besede: cosmic rays, ultra-high-energy cosmic radiation, cosmic ray sources, cosmic ray showers, cosmic ray detectors, cosmic ray astronomy, extragalactic astronomy
Objavljeno v RUNG: 05.02.2021; Ogledov: 2401; Prenosov: 0
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133.
Evidence for a supergalactic structure of magnetic deflection multiplets of ultra-high-energy cosmic rays
R. U. Abbasi, Mitsuhiro Abe, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, Douglas R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, izvirni znanstveni članek

Opis: Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy–angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Ključne besede: extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray sources
Objavljeno v RUNG: 05.02.2021; Ogledov: 2493; Prenosov: 126
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