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

TL;DR

This paper investigates the accidental background in the JSNS$^2$ experiment, quantifying its rate and implications for sterile neutrino searches using muon decay-at-rest neutrinos.

Contribution

It provides the first detailed measurement and analysis of the accidental background rate in the JSNS$^2$ experiment.

Findings

Accidental background rate is (9.29±0.39)×10^{-8} per spill.

Background rate is comparable to the expected signal rate.

Results inform background mitigation strategies for neutrino detection.

Abstract

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.