A search for the anomalous events detected by ANITA using the Pierre Auger Observatory

Abstract

A dedicated search for upward-going air showers at zenith angles exceeding $110^{\circ }$ and energies $E>0.1$ EeV has been performed using the Fluorescence Detector of the Pierre Auger Observatory. The search is motivated by two "anomalous" radio pulses observed by the ANITA flights I and III which appear inconsistent with the Standard Model of particle physics. Using simulations of both regular cosmic ray showers and upward-going events, a selection procedure has been defined to separate potential upward-going candidate events and the corresponding exposure has been calculated in the energy range [0.1-33] EeV. One event has been found in the search period between 1 Jan 2004 and 31 Dec 2018, consistent with an expected background of $0.27\pm 0.12$ events from mis-reconstructed cosmic ray showers. This translates to an upper bound on the integral flux of $(7.2\pm 0.2)\times 10^{-21}$ cm${}^{-2}$ sr${}^{-1}$ y${}^{-1}$ and $(3.6\pm 0.2)\times 10^{-20}$ cm${}^{-2}$ sr${}^{-1}$ y${}^{-1}$ for an $E^{-1}$ and $E^{-2}$ spectrum, respectively. An upward-going flux of showers normalized to the ANITA observations is shown to predict over 34 events for an $E^{-3}$ spectrum and over 8.1 events for a conservative $E^{-5}$ spectrum, in strong disagreement with the interpretation of the anomalous events as upward-going showers.

10+5 Pages of Manuscript plus Supplemental Material, 3+8 figures, Accepted for publication in Physical Review Letters

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• Particle Astrophysics with High and Ultrahigh Energy Neutrinos