Earth regeneration of solar neutrinos at SNO and Super-Kamiokande - art. no. 073009

We analyze the 1258-day Super-Kamiokande day and night solar neutrino energ y spectra with various chi (2) definitions. The best-fit lies in the large mixing angle (LMA) re-ion at (Deltam(2), tan(2)theta) = (5.01 x 10(-5) eV(2 ) 0.60), independently of whether systematic errors are included in the chi (2) definition. We compare the exclusion and allowed regions from the diff erent definitions and choose the most suitable definition to predict the re gions from SNO at the end of three years of data accumulation. We first wor k under the assumption that Super-Kamiokande "sees" a flux-suppressed flat energy spectrum. Then, we consider the possibility of each one of the three Mikheyev-Smirnov-Wolfenstein regions being the solution to the solar neutr ino problem. We find that the exclusion and allowed regions for the flat sp ectrum hypothesis and the LMA and low probability, low mass solutions are a like. In three years, we expect SNO to find very similar regions to that ob tained by Super-Kamiokande. We evaluate whether the zenith angle distributi on at SNO with optimum binning will add anything to the analysis of the day and night spectra; for comparison, we show the results of our analysis of the 1258-day zenith angle distribution from Super-Kamiokande, for which the best-fit parameters are (Am-2, tan(2)theta) = (5.01 x 10(-1) eV(2), 0.56).