Light unstable sterile neutrino

Abstract

The three massless active (doublet) neutrinos may mix with two heavy and one light sterile (singlet) neutrino so that the induced masses and mixings among the former are able to explain the present data on atmospheric and solar neutrino oscillations. If the LSND result is also to be explained, one active neutrino mass eigenstate must mix with the light sterile neutrino, and the fit is improved if the latter also decays quickly enough to evade the CDHSW data. A specific model is proposed with the spontaneous and soft explicit breaking of a new global U(1)_S symmetry so that a sterile neutrino will decay into an active antineutrino and a nearly massless pseudo Majoron.