ON THE MSW νe → νs TRANSITION SOLUTION OF THE SOLAR NEUTRINO PROBLEM

We study the stability of the two–neutrino MSW solution of the solar neutrino problem, corresponding to solar νe transitions into sterile neutrino, νe → νs, with respect to changes of the total fluxes of 8B and 7Be neutrinos, ΦB and ΦBe. For any value of ΦBe from the interval 0.7ΦBP Be ≤ ΦBe ≤ 1.3ΦBP Be (for ΦBe = 0.7ΦBP Be ) the νe → νs MSW transitions provide at 95% C.L. a description of the existing solar neutrino data for 0.40 (0.39) ΦBP B ∼< ΦB ∼< 36 (40)ΦBP B , ΦBP B and ΦBP Be being the fluxes in the solar model of Bahcall–Pinsonneault from 1992. The corresponding allowed regions of values of the parameters ∆m2 and sin 2θ, characterizing the solar neutrino transitions, are derived. The physical implications of the found MSW νe → νs solutions for the future solar neutrino experiments are considered as well. ∗Also at: Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, BG–1784 Sofia, Bulgaria.