Status of the Gribov–Pontecorvo solution to the solar neutrino problem

We discuss the status of the Gribov–Pontecorvo (GP) solution to the solar neutrino problem. This solution naturally appears in bimaximal neutrino mixing and reduces the solar and atmospheric neutrino problems to vacuum oscillations of three active neutrinos. The GP solution predicts an energy-independent suppression of the solar neutrino flux. It is disfavoured by the rate of the Homestake detector, but its statistical significance greatly improves, when the chlorine rate and the boron neutrino flux are slightly rescaled, and when the Super-Kamiokande neutrino spectrum is included in the analysis. Our results show that rescaling of the chlorine signal by only 10% is sufficient for the GP solution to exist, if the boron–neutrino flux is taken 10–20% lower than the SSM prediction. The regions allowed for the GP solution in the parameter space are found and observational signatures of this solution are discussed.