Constraints on the diffuse high-energy neutrino flux from the third flight of ANITA

TL;DR

The third flight of ANITA searched for ultra-high-energy neutrinos via radio signals in Antarctic ice, finding one candidate event consistent with background but still compatible with neutrino origin.

Contribution

This paper reports the first results from ANITA-III, providing constraints on the diffuse high-energy neutrino flux with a novel radio detection method.

Findings

Detected one event consistent with background expectations.

Candidate event remains compatible with a neutrino hypothesis.

Set new limits on the diffuse high-energy neutrino flux.

Abstract

The Antarctic Impulsive Transient Antenna (ANITA), a NASA long-duration balloon payload, searches for radio emission from interactions of ultra-high-energy neutrinos in polar ice. The third flight of ANITA (ANITA-III) was launched in December 2014 and completed a 22-day flight. We present the results of three analyses searching for Askaryan radio emission of neutrino origin. In the most sensitive of the analyses, we find one event in the signal region on an expected a priori background of $0.7^{+0.5}_{-0.3}$. Though consistent with the background estimate, the candidate event remains compatible with a neutrino hypothesis even after additional post-unblinding scrutiny.