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$^2$.
Highlights
Neutral current quasielastic interaction (NCQE) of atmospheric neutrinos with 16O is one of the major interaction channels in water based neutrino detectors for neutrinos with several hundred MeV energy [1]
In this paper we report the first measurement of NCQE cross section using atmospheric neutrinos at Super-Kamiokande (SK)
We report the first measurement of the NCQE cross section on oxygen using atmospheric neutrinos
Summary
Neutral current quasielastic interaction (NCQE) of atmospheric neutrinos with 16O is one of the major interaction channels in water based neutrino detectors for neutrinos with several hundred MeV energy [1]. In water Cherenkov detectors such as Super-Kamiokande (SK), where e=γ discrimination is feasible but still challenging, NCQE interactions of atmospheric neutrinos with oxygen form a significant background to SRN searches as well as other rare signal searches [4,5,6,7]. No previous measurement of this process has been performed using the atmospheric neutrino flux, where NCQE interactions are of relevance for SRN searches. We report the first measurement of the NCQE cross section on oxygen using atmospheric neutrinos. This measurement is important for SRN searches in future water Cherenkov experiments such as SK-Gd [12,13] and HyperKamiokande [14].
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