LEFT-RIGHT SYMMETRY AND NEUTRINO STABILITY

We consider a left-right symmetric model in which neutrinos acquire ma ss due to the spontaneous violation of both the gauged B - L and a glo bal U(1) symmetry broken by the vacuum expectation value (VEV) of a ga uge singlet scalar boson [sigma]. For suitable choices of [sigma] cons istent with all laboratory and astrophysical observations neutrinos wi ll be unstable against majoron emission. All neutrino masses in the ke V to MeV range are possible, since the expected neutrino decay lifetim es can be short enough to dilute their relic density below the cosmolo gically required level. A wide variety of possible new phenomena, asso ciated to the presence of left-right symmetry and/or the global symmet ry at the TeV scale, could therefore be observable, without conflict w ith cosmology. The latter includes the possibility of invisibly decayi ng higgs bosons, which can be searched at LEP, NLC and LHC.