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Ključne besede: ultra-high energy cosmic rays, extensive air showers, Pierre Auger Observatory, water Cherenkov detectors, detector calibration, hodoscope-based calibration
Objavljeno v RUNG: 11.09.2020; Ogledov: 4083; Prenosov: 119
Celotno besedilo (1,39 MB)

Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, inclined air showers, muon number fluctuations
Objavljeno v RUNG: 24.07.2020; Ogledov: 3275; Prenosov: 77
Celotno besedilo (630,96 KB)

Ključne besede: Pierre Auger Observatory, extensive air showers, event reconstruction, deep learning
Objavljeno v RUNG: 16.06.2020; Ogledov: 3493; Prenosov: 83
Celotno besedilo (1,16 MB)

Opis: Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment includes a surface detector (SD) array and three fluorescence detector (FD) stations. The FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye (HiRes) experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tube pixels. To obtain the EAS parameters with high accuracy, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of the new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.
Ključne besede: Ultra high energy cosmic rays, Extensive air showers, Air fluorescence light detectors
Objavljeno v RUNG: 19.05.2020; Ogledov: 3353; Prenosov: 0
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Opis: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory is the largest experiment that can detect the extensive air showers produced when the cosmic rays and neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply- penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We have established a complete chain of criteria to first select the inclined events among the sample of all events triggering the Infilled array, and then identifying those that have a large electromagnetic component at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017. Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor, k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Ključne besede: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled array
Objavljeno v RUNG: 03.10.2019; Ogledov: 5810; Prenosov: 155
Celotno besedilo (6,02 MB)