Precise Measurement of the Solar Neutrino Day/Night and Seasonal Variation in Super-Kamiokande-I

The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kamiokande-I was fit to the variations expected from active two-neutrino oscillations. The best fit in the Large Mixing Angle solution has a mixing angle of tan^2theta=0.55 and a mass squared difference of Deltam^2=6.3times10^-5eV^2 between the two neutrino mass eigenstates. The fitted day/night asymmetry of -1.8+-1.6(stat)+1.3-1.2(syst)% has improved statistical precision over previous measurements and agrees well with the expected asymmetry of -2.1%.