MAJORON DECAY IN MATTER

It is well known that matter can significantly alter the picture of ne utrino oscillation [1] or neutrino decay [2]. Here we show that the pr esence of dense matter induces also the decay of massless majoron, a G oldstone boson associated with the spontaneous lepton number violation , into a couple of neutrinos with the same (or in some cases also oppo site) helicites. We calculate the rates of such matter induced majoron decays in various cases, depending on the neutrino type and the chemi cal content of the medium, and analyse their properties.