Speaker
Description
In this talk, we report the first diffuse ultrahigh energy (UHE) neutrino search using all five stations of the Askaryan Radio Array (ARA) at the South Pole. ARA searches for radio-frequency Askaryan emission from particle showers initiated by neutrino interactions in Antarctic ice. This search uses data collected from 2013 through 2023, corresponding to 10.6 years of livetime and a dataset approximately three times larger than that used in previous ARA neutrino searches. The analysis of the data reaches 28% efficiency for a diffuse neutrino flux corresponding to the current experimental upper limits. No neutrino candidates are observed after all event selections, consistent with an expected background of 0.13 ± 0.01 (stat.) −0.06 + 0.05 (syst.) events. From this result, we derive a new upper limit on the diffuse UHE neutrino flux, which is the most stringent above 50 EeV. This work combines data from all independent ARA stations and demonstrates a multi-station search strategy relevant for other in-ice radio neutrino detectors, including RNO-G, which is under construction, and the planned IceCube-Gen2 Radio array.