Implications of the Sno and the Homestake Results for the Borexino Experiment

Using the recent result of the SNO solar neutrino experiment, we have demonstrated in a model independent way that the contribution of Be and other medium energy neutrinos to the event rate of the Homestake experiment is 4σ smaller than the BP2000 SSM prediction. We have considered the implications of this result for the future BOREXINO experiment. The recently published first data of the SNO experiment [1] combined with the data of the Super-Kamiokande solar neutrino experiment [2] present clear evidence of the presence of νμ and/or ντ in the flux of high energy solar neutrinos on the Earth. The large up-down asymmetry of high energy atmospheric muon events, discovered by the Super-Kamiokande collaboration [3], constitutes a model independent evidence in favor of oscillations of atmospheric neutrinos. The data of all solar and atmospheric neutrino experiments can be described by practically decoupled two-neutrino oscillations driven by the mixing of three neutrinos with neutrino mass squared differences that satisfy the hierarchy ∆m2sol ≪ ∆m 2 atm (see [4]). There exist at present indications in favor of ν̄e → ν̄μ oscillations that were obtained in the accelerator experiment LSND [5]. If the data of the LSND experiment will be confirmed, we must assume that (at least) four mixed neutrinos with small masses exist in nature and that flavor neutrinos can transfer into sterile states. A check of the LSND result is going to be achieved by the MiniBooNE experiment [6], scheduled to start in 2002. The SNO result triggered several new global analysis of the data of all solar neutrino experiments [7, 8] . After the Super-Kamiokande measurement [2] of the energy spectrum of recoil electrons and the zenith angle dependence of the flux of solar neutrinos large mixing angle MSW solutions became the most favorable fits [9] of all pre-SNO solar neutrino data ([2, 10, 11, 12, 13]). Also at Joint Institute for Nuclear Research, Dubna, Russia.