1. Searches for UHE neutrinos and upward-going showers at the Pierre Auger ObservatoryJaime Alvarez-Muňiz, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, published scientific conference contribution Abstract: The Pierre Auger Observatory, as a key actor in multi-messenger astronomy, is playing a crucial role in searching for and following-up cosmic phenomena across different channels. Data from the Observatory have been utilized for nearly 20 years to search for showers induced by Ultra-High-Energy (UHE) neutrinos with energies exceeding 0.1 EeV. Neutrino-induced showers at high zenith angles are likely to develop deep in the atmosphere, resulting in a significant electromagnetic component that distinguishes them from the cosmic-ray background. This enables the identification of candidate events from both neutrinos interacting in the atmosphere and Earth-skimming τ neutrinos. Searches have been conducted for both diffuse and point sources using data collected by the Surface Detector, a large array of over 1660 water-Cherenkov stations spread over an area of 3000 square km. Additionally, the Fluorescence Detector consisting of 27 telescopes has been employed to search for upward-developing air showers, as predicted by several interpretations of the 'anomalous' events detected by the ANITA detector. In this contribution, we summarize the main results obtained in these searches and discuss their astrophysical implications.
Keywords: ulti-messenger astronomy, ultra-high-energy neutrino search, down-going neutrinos, Earth-skimming τ neutrinos, search for upward-developing air showers, ANITA detector, Pierre Auger Observatory
Published in RUNG: 24.03.2025; Views: 312; Downloads: 6
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2. SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORYMarta Trini, 2019, 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 .
Keywords: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled
array
Published in RUNG: 03.10.2019; Views: 6175; Downloads: 157
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3. Ultrahigh energy neutrino follow-up of Gravitational Wave Event GW150914 with the Pierre Auger ObservatoryJaime Alvarez-Muňiz, Francisco Pedreira, Zlatka Zas, Pablo Pieroni, Marta Trini, Lili Yang, treatise, preliminary study, study Keywords: UHE neutrinos, SD detector, Gravitational Waves
Published in RUNG: 29.11.2016; Views: 6504; Downloads: 0
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