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11.
SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORY
Marta Trini, doctoral dissertation

Abstract: 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 .
Found in: ključnih besedah
Summary of found: ...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...
Keywords: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled array
Published: 03.10.2019; Views: 1533; Downloads: 44
.pdf Fulltext (6,02 MB)

12.
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 Observatory
Gašper Kukec Mezek, 2018, published scientific conference contribution

Abstract: 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 besedah
Summary of found: ...has the possibility to detect extensive air showers with an array of surface water-Cherenkov stations...
Keywords: astroparticle physics, ultra-high energy cosmic rays, extensive air showers, mass composition, Pierre Auger Observatory, fluorescence telescopes, water-Cherenkov stations
Published: 24.05.2019; Views: 909; Downloads: 47
.pdf Fulltext (573,00 KB)

13.
New air fluorescence detectors employed in the Telescope Array experiment
J. P. Lundquist, H. Tokuno, 2012, original scientific article

Abstract: 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.
Found in: ključnih besedah
Summary of found: ...USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment... ...air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies...
Keywords: Ultra high energy cosmic rays, Extensive air showers, Air fluorescence light detectors
Published: 19.05.2020; Views: 324; Downloads: 0
.pdf Fulltext (1,44 MB)

14.
Highlights from the Pierre Auger Observatory
Lukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Antonella Castellina, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...ultra-high energy cosmic rays, extensive air showers, Pierre Auger Observatory...
Keywords: ultra-high energy cosmic rays, extensive air showers, Pierre Auger Observatory
Published: 16.06.2020; Views: 322; Downloads: 18
.pdf Fulltext (4,92 MB)

15.
Measurement of the fluctuations in the number of muons in inclined air showers with the Pierre Auger Observatory
Lukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Felix Riehn, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...ultra-high energy cosmic rays, Pierre Auger Observatory, inclined air showers,...
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, inclined air showers, muon number fluctuations
Published: 24.07.2020; Views: 295; Downloads: 13
.pdf Fulltext (630,96 KB)

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Estimating the Depth of Shower Maximum using the Surface Detectors of the Pierre Auger Observatory
Lukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Lili Yang, Serguei Vorobiov, Marta Trini, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Carlos José Todero Peixoto, 2019, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), extensive air showers, Auger Surface Detector...
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), extensive air showers, Auger Surface Detector (SD) array, depth of shower maximum
Published: 21.12.2020; Views: 52; Downloads: 3
.pdf Fulltext (850,78 KB)

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