Sensitivity to Atypical Tau Initiated Air Showers For a High-Altitude Optical Cherenkov Detector

TL;DR

This paper evaluates the potential of high-altitude optical Cherenkov detectors, like EUSO-SPB2 and POEMMA, to detect atypical tau-initiated air showers possibly linked to new physics beyond the standard model.

Contribution

It analyzes the sensitivity of upcoming balloon and satellite-based Cherenkov detectors to rare upward air showers potentially caused by astrophysical neutrinos or new physics.

Findings

Cherenkov detectors can potentially observe these rare events.

Detection sensitivity depends on detector altitude and orientation.

Results support future experiments to test anomalous upward air showers.

Abstract

The ANITA collaboration has recently announced the supposed observation of two upward going cosmic ray showers at earth emergence angles $27^{\circ}$ and $35^{\circ}$ with reconstructed energy $\sim$0.6~EeV. Upward air showers (UAS) are expected from tau leptons resulting from the interaction of astrophysical neutrinos inside the Earth. However, at emergence angles larger than $20^{\circ}$, the probability of tau emergence from a neutrino is less than $10^{-7}$, which makes a standard model explanation for these signals difficult. If confirmed by other experiments, these energetic events would strengthen the argument for physics beyond the standard model. Both the proposed EUSO-SPB2 and the POEMMA instruments will be equipped with optical Cherenkov detectors in order to measure the Cherenkov emission from UAS, which, if aimed low enough below the horizon, could, in principle, capture these events as well. An observation in the Cherenkov channel would help to rule out anthropogenic and other explanations for these events. We present here the sensitivity to the ANITA anamolous events for a balloon based and a satellite based Cherenkov detector, as could be realized in the upcoming EUSO-SPB2 mission and the proposed POEMMA mission, respectively.