Characterization of the correlated background for a sterile neutrino search using the first dataset of the JSNS$^2$ experiment

TL;DR

This paper characterizes the correlated background in the JSNS$^2$ sterile neutrino search using initial commissioning data and discusses potential improvements in pulse shape discrimination to reduce cosmic ray-induced backgrounds.

Contribution

It provides the first estimate of correlated background in JSNS$^2$ and explores methods to improve background suppression for future experiments.

Findings

Estimated the correlated background from commissioning data

Identified potential pulse shape discrimination improvements

Discussed future prospects for background reduction

Abstract

JSNS$^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that is searching for sterile neutrinos via the observation of $\bar{\nu}_{\mu} \to \bar{\nu}_{e}$ appearance oscillations using muon decay-at-rest neutrinos. Before dedicated data taking in the first-half of 2021, we performed a commissioning run for 10 days in June 2020. Using the data obtained in this commissioning run, in this paper, we present an estimate of the correlated background which imitates the $\bar{\nu}_{e}$ signal in a sterile neutrino search. In addition, in order to demonstrate future prospects of the JSNS$^2$ experiment, possible pulse shape discrimination improvements towards reducing cosmic ray induced fast neutron background are described.