Astrophysical and Terrestrial Constraints on Singlet Majoron Models

The general Lagrangian containing the couplings of the Higgs scalars to Majorana neutrinos is presented in the context of singlet Majoron models with intergenerational mixings. The analytical expressions for the coupling of the Majoron field to fermions are derived within these models. Astrophysical considerations imply severe restrictions on the parameters of the model if the singlet Majoron model with three generations is assumed to be embedded in grand unified theories. Bounds that originate from analyzing possible charged lepton-violating decays in terrestrial experiments are also discussed. In particular, we find that experimental searches for muon decays by Majoron emission cannot generally be precluded by astrophysical requirements.