First Array-Wide Search for Diffuse UHE Neutrinos with the Askaryan Radio Array

Abstract

The Askaryan Radio Array (ARA) is an ultrahigh energy (UHE) neutrino detector at the South Pole, designed to search for radio pulses emitted by neutrino-initiated particle showers in ice. ARA consists of an array of five autonomous stations with 2 km spacing. Each station consists of 16 radio antennas embedded ${\sim}200$ m deep in the ice that are sensitive to either vertically- or horizontally-polarized signals. Radio arrays like ARA represent a cost-efficient means of achieving the enormous detection $O(10~\text{km}^3)$ volumes necessary for UHE neutrino detection. This contribution presents the current status of the first-ever array-wide search for UHE neutrinos, leveraging ARA's unprecedented ${\sim}28$ station-years of livetime. This search will have the best sensitivity of any neutrino detector above $3$ EeV, sufficient to probe the $220$ PeV flux inferred from KM3NeT's observation of KM3-230213A. Importantly, this study demonstrates the feasibility of array-wide neutrino searches, which are necessary for next-generation detectors, like RNO-G (35 stations planned) and IceCube-Gen2 Radio (361 stations proposed), to achieve their design sensitivity. We discuss the progress towards a fully analyzed sample and improvements to ARA's detector characterization and analysis sensitivity.