Sensitivity of the As-Built Askaryan Radio Array to Ultra-High Energy Neutrinos

TL;DR

This paper evaluates the sensitivity of the Askaryan Radio Array to ultra-high energy neutrinos, showing it has competitive detection capabilities and discussing implications for future experiments.

Contribution

It introduces an enhanced simulation pipeline and provides the first comprehensive sensitivity analysis of ARA over a decade of data.

Findings

ARA achieves world-leading sensitivity above 10^19 eV.

Up to 13 neutrinos could have been observed in 2013-2023 at trigger-level.

Secondary particles contribute up to 30% of total acceptance at high energies.

Abstract

The Askaryan Radio Array (ARA) is an ultra-high energy (UHE) neutrino observatory designed to detect the impulsive radio waves produced by relativistic particle cascades in the Antarctic glacial ice. Using a significantly enhanced simulation pipeline, which adds data-driven detector simulations and fully incorporates secondary particle production, we calculate the trigger-level acceptance of the entire array. We compare the resulting trigger-level sensitivity to constraints on the UHE neutrino flux from other detectors. Given its exposure from 2013 to 2023, we find that ARA achieves a world-leading sensitivity above about $10^{19}$ eV, depending on the details of the event selection used in a search. Moreover, we find that up to 13 neutrinos are predicted to have been observed in this period at trigger-level, assuming the most optimistic neutrino flux models. We show that observations of secondary particles account for up to 30\% of the total acceptance starting at $10^{19}$ eV, and we explore the potential signatures and implications of both multi-pulse (from direct and refracted pulses and/or from secondary particle interactions) and multi-station events. Finally, we comment on the implications of this study for the design of next-generation UHE neutrino experiments, in particular IceCube-Gen2 Radio.