Violation of the equivalence principle in the light of the SNO and SK solar neutrino results

Abstract

The Sudbury Neutrino Observatory (SNO) result on charged current deuteron disintegration, the Super Kamiokande 1258-day data on electron scattering, and other solar neutrino results are used to reexamine the model of neutrino oscillations driven by a violation of the equivalence principle. We use a χ² minimization technique to examine oscillations between the ν_e and another active neutrino, both massless, and find that within the standard solar model the fit to the SNO and Super-Kamiokande spectra is moderately good while a very good fit is obtained when the absolute normalizations of the ⁸B and ³He+p (hep) neutrino fluxes are allowed to vary. The fit to the total rates from the different experiments is not encouraging but when the rates and spectra are considerd together the situation is much improved. The best fit prefers maximal mixing, essentially no hep neutrinos, and a 23% reduction in the ⁸B neutrino flux. We remark on the expectations of the violation of the equivalence principle model for the neutral current measurements at SNO.