How Large Is the $^7{Be}$ Neutrino Flux from the Sun ?

Abstract

On the basis of present solar neutrino observations and relaxing the constraints from solar models it is possible that most (or nearly all) of the flux of electron neutrinos detected comes from electron capture in $^7{Be}$. These solutions arise from neutrino oscillations in which $ν_e$ $-$ $ν_τ$ mixing suppresses high energy $ν_e$ and $ν_e - ν_μ$ mixing suppresses low energy $ν_e$ as qualitatively suggested from some SO(10) grand unified models. The importance of future observations is emphasized.