Do [formula omitted]e come out from the sun?

Abstract

From the available data on the background of the Kamioka experiment we find serious constraints on the possibility that solar neutrinos transform into ν e. For energy E ν ⩾ 10.6 MeV the ν e flux cannot exceed 6.1 × 10 4 cm −2 s −1. Assuming the ν e energy distribution to be given by the 8B decay spectrum, the bound gets more strict by a factor two. We discuss the relevance of these bounds for hybrid solutions of the solar neutrino problem.