Homestake result, sterile neutrinos and low energy solar neutrino experiments

  • 21 July 2003
Abstract
The large mixing (LMA) MSW solution predicts ~2-sigma higher Ar-production rate, Q_{Ar}, than the Homestake result. Also there is no apparent upturn of the spectrum (R=N_obs/N_SSM) at low energies in SNO and Super-Kamiokande (SK). Both these facts can be explained if a light, \Delta m^2_{01} ~ (2 - 20)10^{-5} eV^2, sterile neutrino exists which mixes very weakly with active neutrinos: sin^2 2\alpha ~ (10^{-5} - 10^{-3}). We perform both the analytical and numerical study of conversion effects in the system of two active neutrinos with the LMA parameters and one weakly mixed sterile neutrino. The presence of sterile neutrino leads to a dip in the survival probability in the intermediate energy range E = (0.5 - 5) MeV thus suppressing the Be, or/and pep, CNO as well as B neutrino fluxes. Apart from diminishing Q_{Ar} it leads also to decrease of the Ge-production rate and may lead to decrease of the BOREXINO signal and CC/NC ratio at SNO. Future studies of the solar neutrinos by SNO, SK, BOREXINO and KamLAND as well as new low energy experiments will allow to check this possibility. We present a general analysis of possible modifications of the LMA energy profile due tomixing with new neutrino states.

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