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 $\nu_e$ $-$ $\nu_\tau$ mixing suppresses high energy $\nu_e$ and $\nu_e - \nu_\mu$ mixing suppresses low energy $\nu_e$ as qualitatively suggested from some SO(10) grand unified models. The importance of future observations is emphasized.