Solar Neutrino Results from Super-Kamiokande

TL;DR

This paper reports precise measurements of solar neutrino flux by Super-Kamiokande, analyzing energy spectrum and time dependence to investigate neutrino oscillations and constrain neutrino properties.

Contribution

First detailed measurement of solar neutrino flux in the 5-20 MeV range with constraints on neutrino oscillation parameters.

Findings

Measured flux of $2.32\pm0.03$(stat)$^{+0.08}_{-0.07}$(syst)$\times10^6$/(cm$^2$s)

No significant zenith angle flux variation observed

Identified two large mixing angle regions consistent with data

Abstract

Super-Kamiokande has measured the solar neutrino flux using elastic neutrino-electron scattering in water. The measured flux is $2.32\pm0.03$(stat)$^{+0.08}_{-0.07}$(syst)$\times10^6$/(cm$^2$s) based on the energy range of 5 to 20 MeV for the recoiling electron. The time-dependence and energy spectrum of the recoiling electrons were studied to search for two-neutrino oscillation signatures. The absence of either significant zenith angle flux variation or distortions of the recoil electron spectrum places strong constraints on neutrino mass difference and mixing. In combination with the flux measurement, two allowed regions at large mixing are found.