Experimental study of the atmospheric neutrino backgrounds for proton decay to positron and neutral pion searches in water Cherenkov detectors

TL;DR

This study uses an artificial neutrino beam to measure atmospheric neutrino backgrounds relevant for proton decay searches in water Cherenkov detectors, providing data that supports background estimation for large-scale experiments.

Contribution

First experimental measurement of atmospheric neutrino backgrounds for proton decay searches using an artificial neutrino beam and a water Cherenkov detector.

Findings

Background rate of about two events per megaton-year for energies below 3 GeV.

Simulation programs accurately reproduce observed neutrino interactions.

Results are applicable to future megaton-scale water Cherenkov detectors.

Abstract

The atmospheric neutrino background for proton decay to positron and neutral pion in ring imaging water Cherenkov detectors is studied with an artificial accelerator neutrino beam for the first time. In total, about 314,000 neutrino events corresponding to about 10 megaton-years of atmospheric neutrino interactions were collected by a 1,000 ton water Cherenkov detector (KT). The KT charged-current single neutral pion production data are well reproduced by simulation programs of neutrino and secondary hadronic interactions used in the Super-Kamiokande (SK) proton decay search. The obtained proton to positron and neutral pion background rate by the KT data for SK from the atmospheric neutrinos whose energies are below 3 GeV is about two per megaton-year. This result is also relevant to possible future, megaton-scale water Cherenkov detectors.