REEXAMINATION OF NEUTRINO OSCILLATION SOLUTIONS TO THE SOLAR-NEUTRINO PROBLEM

A deficit of solar neutrinos compared to the standard solar model prediction has been measured in both the Homestake and Kamiokande-II experiments, with quite different detectors. We analyze the parameter space for oscillations of two neutrinos to find regions that can explain both experiments. Long-wavelength vacuum oscillation solutions are found with delta-m2 congruent-to 0.5-2.5 x 10(-10) eV2 and sin2 2-theta greater-than-or-similar-to 0.7. Matter-enhanced oscillation solutions are found for (i) nonadiabatic transitions having delta-m2-theta-2 almost-equal-to 10(-8) eV2 and and delta-m2 almost-equal-to 3 x 10(-8) -2 x 10(-5) eV2, and (ii) adiabatic transitions having delta-m2 almost-equal-to 10(-7) -10(-4) eV2 with sin2 2-theta greater-than-or-approximately 0.5. The two-neutrino long-wavelength and matter-enhanced solutions predict Ga-71 measurements in the ranges 50-80 and 5-115 solar-neutrino units (SNU), respectively, compared to 130 SNU without oscillations. We emphasize the distinctive features of each solution, including their predictions for future nu-e scattering experiments and detectable seasonal variations in the long-wavelength solutions. We also find the range of three-neutrino vacuum oscillation solutions.