On the MSW $ν_e \to ν_s$ transition solution of the solar neutrino problem

Abstract

We study the stability of the two--neutrino MSW solution of the solar neutrino problem, corresponding to solar $ν_e$ transitions into sterile neutrino, $ν_e \rightarrow ν_s$, with respect to changes of the total fluxes of $^{8}$B and $^{7}$Be neutrinos, $Φ_{\rm B}$ and $Φ_{\rm Be}$. For any value of $Φ_{\rm Be}$ from the interval $0.7Φ^{\rm BP}_{\rm Be}\leq Φ_{\rm Be} \leq 1.3Φ^{\rm BP}_{\rm Be}$ (for $Φ_{\rm Be} = 0.7Φ^{\rm BP}_{\rm Be}$) the $ν_e \rightarrow ν_{s}$ MSW transitions provide at 95\% C.L. a description of the existing solar neutrino data for $0.40~(0.39)~Φ^{\rm BP}_{\rm B} \ltap Φ_{\rm B} \ltap 36~(40)Φ^{\rm BP}_{\rm B}$, $Φ^{\rm BP}_{\rm B}$ and $Φ^{\rm BP}_{\rm Be}$ being the fluxes in the solar model of Bahcall--Pinsonneault from 1992. The corresponding allowed regions of values of the parameters \dm2 and \sn2, characterizing the solar neutrino transitions, are derived. The physical implications of the found MSW $ν_e \rightarrow ν_s$ solutions for the future solar neutrino experiments are considered as well.