# Measurement of neutrino-oxygen neutral-current quasi-elastic cross section using atmospheric neutrinos at Super-Kamiokande

## TL;DR

This paper reports the first measurement of the neutrino-oxygen neutral-current quasi-elastic cross section using atmospheric neutrinos at Super-Kamiokande, providing new data crucial for background estimation in supernova relic neutrino searches.

## Contribution

It presents the first experimental measurement of the NCQE cross section on oxygen with atmospheric neutrinos at Super-Kamiokande, filling a key gap in neutrino interaction data.

## Key findings

- Measured NCQE cross section: (1.01 ± 0.17 (stat.) +0.78/-0.30 (sys.)) × 10^{-38} cm^2.
- Observed 117 events with an expected signal of 71.9 and background of 53.1.
- Used 2,778 live days of SK-IV data with a 22.5 kiloton water volume.

## Abstract

Neutral current (NC) interactions of atmospheric neutrinos on oxygen form one of the major backgrounds in the search for supernova relic neutrinos with water-based Cherenkov detectors. The NC channel is dominated by neutrino quasi-elastic (NCQE) scattering off nucleons inside $^{16}$O nuclei. In this paper we report the first measurement of NCQE cross section using atmospheric neutrinos at Super-Kamiokande (SK). The measurement used 2,778 live days of SK-IV data with a fiducial volume of 22.5 kiloton water. Within the visible energy window of 7.5-29.5 MeV, we observed $117$ events compared to the expected $71.9$ NCQE signal and $53.1$ background events. Weighted by the atmospheric neutrino spectrum from 160 MeV to 10 GeV, the flux averaged NCQE cross section is measured to be $(1.01\pm0.17(\text{stat.})^{+0.78}_{-0.30}(\text{sys.}))\times10^{-38}$ cm$^2$.