Pulse Shape Discrimination in JSNS²

JSNS² (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of ν̄μ → ν̄ₑ appearance oscillations using neutrinos with muon decay-at-rest. For this search, rejecting cosmic-ray-induced neutron events by Pulse Shape Discrimination (PSD) is essential because the JSNS² detector is located above ground, on the third floor of the building. We have achieved 95$%$ rejection of neutron events while keeping 90$%$ of signal, electron-like events using a data driven likelihood method.