COSMOLOGICALLY INTERESTING NEUTRINO DECAY IN SUPERSYMMETRY WITH BROKEN R-PARITY

We show that in the minimal supersymmetric standard model with broken R-parity, for which the lepton number violating couplings induce neutrino masses and transition magnetic moments at one loop, the radiative decay of the heaviest neutrino nu-h --> nu-l + gamma can have in a natural way a typical lifetime tau almost-equal-to 10(23) s if the mass scale for nu-h is almost-equal-to 30 eV. In this case, nu-h can provide the missing mass of the universe, and its radiative decay happens at the required rate to explain several astrophysical observations of the H-alpha emission lines and ionization of the HI clouds. We discuss scenarios in which nu-h is mainly nu-mu or nu-tau.