First results from the search for an excess of ν ¯ e events in JSNS 2

The JSNS 2 (J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source) experiment at the Material and Life Science Facility (MLF) of J-PARC is designed to directly test an excess on ν ¯ e events which was indicated by the Liquid Scintillator Neutrino Detector (LSND). The combination of a short-pulsed proton beam and a gadolinium-loaded liquid scintillator provides an excellent signal-to-noise ratio. In this article, we report the first results of a direct test based on data collected in 2022. After applying all event selection criteria, two events are observed, consistent with the expected background of 2.3 ± 0.4 events. No excess of ν ¯ e events are seen in this report, however the expected number of events due to LSND anomaly is 1.1 ± 0.5 , thus this result is not yet conclusive. Data taking has been ongoing since 2021 and will continue in future runs. In addition, a new far detector has recently been constructed for the second phase experiment, JSNS 2 -II, marking an important milestone toward forthcoming measurements.