Search for upward-going showers with the Pierre Auger Observatory

Abstract

Motivated by the ANITA report of pulses compatible with upward-going extensive air showers, we present a recent search for such showers using the Pierre Auger Observatory. The dataset, registered using the fluorescence detector of the Observatory, is scanned to identify showers ascending from the ground. Consistent with the exit angles reported from the first and third ANITA flights, we focus on shower geometries that are incompatible with Standard Model interactions of neutrinos in the Earth. We present the effective area of the Observatory to generic upward-going showers as a function of shower energy and altitude. This can be used to constrain predictions based on physics beyond Standard Model and the upgoing-shower interpretation of the ANITA results. To demonstrate the method, we calculate limits to the production rate of tau leptons near the ground emerging under a range of exit angles.