Solar neutrinos: What is next?

Abstract

Status of the solar neutrino studies after KamLAND and the SNO salt phase experiment is summarized. The present data determine quantitatively the physical picture of the solar neutrino conversion. The next step in the field will be related to further checks of the LMA MSW solution, precision measurements of the oscillation parameters, searches for sub-leading effects and studies of solar neutrino fluxes. The predictions for the forthcoming measurements are given which include the spectral distortion and CC/NC ratio at SNO, the Day-Night asymmetry, the KamLAND spectrum and rate. The Homestake result is about ∼ 2σ lower than the Ar-production rate, Q Ar , predicted by the LMA MSW solution. Also there is no apparent "upturn" of the energy spectrum (R ≡ N obs /N SSM ) at low energies in SNO and Super-Kamiokande. Both these facts can be explained if a light sterile neutrino exists which mixes very weakly with active neutrinos. Future studies of the solar neutrinos by SNO, SK, BOREXINO and KamLAND as well as by the new low energy experiments will allow us to check this possibility. In connection to future precision measurements of the solar neutrino fluxes effects of the non-zero 13-mixing are considered.This text is based on the papers hep-ph/0307266 and hep-ph/0309299 written in collaboration with P.C. de Holanda.Dedicated to Jose who knows why we are writing proceedings... After SNO salt resultsThe