Super-Kamiokandeʼs Solar ν Results

Super-Kamiokande observed 57,700 recoil electrons from solar 8B and hep neutrino–electron scattering between 3.489 and 19.489 MeV kinetic energy in 3,904 live days. The interaction rate is 45.1±0.7% of the rate expected from a pure νe 8B flux of 5.25×106/cm2s (and a hep flux of 7.88×103/cm2s). The observed recoil electron spectrum favors a flat suppression over distortions predicted by standard neutrino flavour oscillation parameters by 1.1 to 1.9σ. The observed day/night variation of −2.8±1.1(stat)±0.5(syst)% is consistent with zero at the 2.3σ level. The oscillation analysis of this data determines the solar neutrino mass2 splitting , consistent within 1.5 to 2σ with KamLANDʼs anti-neutrino measurement.