On the MSW ${\nu }_e\to {\nu }_s$ 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 ${\nu }_e$ transitions into sterile neutrino, ${\nu }_e\to {\nu }_s$, with respect to changes of the total fluxes of ${}^8$B and ${}^7$Be neutrinos, ${\Phi }_{\mathrm{B}}$ and ${\Phi }_{\mathrm{Be}}$. For any value of ${\Phi }_{\mathrm{Be}}$ from the interval $0.7{\Phi }_{\mathrm{Be}}^{\mathrm{BP}}\le {\Phi }_{\mathrm{Be}}\le 1.3{\Phi }_{\mathrm{Be}}^{\mathrm{BP}}$ (for ${\Phi }_{\mathrm{Be}}=0.7{\Phi }_{\mathrm{Be}}^{\mathrm{BP}}$) the ${\nu }_e\to {\nu }_s$ MSW transitions provide at 95\% C.L. a description of the existing solar neutrino data for $0.40(0.39){\Phi }_{\mathrm{B}}^{\mathrm{BP}}\text{ltap}{\Phi }_{\mathrm{B}}\text{ltap}36(40){\Phi }_{\mathrm{B}}^{\mathrm{BP}}$, ${\Phi }_{\mathrm{B}}^{\mathrm{BP}}$ and ${\Phi }_{\mathrm{Be}}^{\mathrm{BP}}$ 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 ${\nu }_e\to {\nu }_s$ solutions for the future solar neutrino experiments are considered as well.

Comments: 23 pages, revtex; texfile and figures available also as one tar-compressed, uuencoded file from ftp://ftp.sns.ias.edu/pub/krastev/STER (first three figures, when unpacked, are 6.9 Mb each !!!)