Neutrino Decay in the Doublet Majoron Model

A new Majoron model is presented within the framework of the seesaw mechanism. Its Higgs sector consists of only doublet representations and the lepton-number violation takes place at the same scale of the electroweak symmetry breaking. This model is different from the singlet- or triplet-Majoron model in several respects: it is free from the $\rho$-parameter constraint and it provides moderately fast neutrino decay, but the constraint from the stellar cooling of red giants is satisfied only with an imposed approximate symmetry. A $\tau$ neutrino as heavy as 10 MeV is possible in this model despite various cosmological and astrophysical constraints.