| Title: | SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORY |
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| Authors: | Trini, Marta (Author)
Zavrtanik, Danilo (Mentor) More about this mentor... 
Alvarez-Muňiz, Jaime (Mentor) More about this mentor... |
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| Files: |  PhDThesis_marta_trini.pdf (6,02 MB)
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| Language: | English |
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| Work type: | Doctoral dissertation (mb31) |
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| Tipology: | 2.08 - Doctoral Dissertation |
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| Organization: | FPŠ - Graduate School |
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| 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 . |
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| Keywords: | astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled
array |
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| Year of publishing: | 2019 |
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| Year of performance: | 2019 |
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| COBISS_ID: | 5457915 |
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| URN: | URN:SI:UNG:REP:XAN3REOT |
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| Views: | 3811 |
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| Downloads: | 136 |
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