SolarB8and hep Neutrino Measurements from 1258 Days of Super-Kamiokande Data

Abstract

Solar neutrino measurements from 1258 days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0--20.0 MeV. The measured solar neutrino flux is $2.32\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{stat}{)}_{\ensuremath{-}0.07}^{+0.08}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{6}{\mathrm{cm}}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}$, which is $45.1\ifmmode\pm\else\textpm\fi{}0.5(\mathrm{stat}{)}_{\ensuremath{-}1.4}^{+1.6}(\mathrm{syst})%$ of that predicted by the BP2000 SSM. The day vs night flux asymmetry $({\ensuremath{\Phi}}_{n}\ensuremath{-}{\ensuremath{\Phi}}_{d})/{\ensuremath{\Phi}}_{\mathrm{average}}$ is $0.033\ifmmode\pm\else\textpm\fi{}0.022(\mathrm{stat}{)}_{\ensuremath{-}0.012}^{+0.013}(\mathrm{syst})$. The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a $90%$ C.L. upper limit of $40\ifmmode\times\else\texttimes\fi{}{10}^{3}{\mathrm{cm}}^{\ensuremath{-}2}{\mathrm{s}}^{\ensuremath{-}1}$, which is 4.3 times the BP2000 SSM prediction.