17 keV neutrino in a singlet-triplet majoron model

Abstract

We investigate the possibility of a cosmologically safe 17 keV neutrino which may have been observed in the decays of tritium, S 35, and C 14 within a singlet-triplet majoron model. Consideration of the leptonic decay of K + and X rays associated with the radiative decay of massive relic neutrinos severely constrains the scale of the spontaneous lepton number violation. It is argued that the mass density of relic 17 keV neutrinos is constrained as Ω v ⩽ 0.05 h −1(0.01/ sin 2 θ) in view of the observed diffuse X ray background.