Study on the accidental background of the JSNS${}^2$ experiment

JSNS${}^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment which searches for sterile neutrinos via the observation of ${\bar{\nu }}_{\mu }\to {\bar{\nu }}_e$ appearance oscillations using muon decay-at-rest neutrinos. The data taking of JSNS${}^2$ have been performed from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is (9.29$\pm 0.39)\times {10}^{-8}$ / spill with 0.75 MW beam power and comparable to the number of searching signals.