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.