Neutrino physics in the Majoron models

Several results related to the Majoron models are presented. Based on a model Lagrangian, the emission of majorons from the supernova SN1987A is analyzed. By requiring the emission not to cool the supernova too rapidly, a constraint is obtained on a combination of the majoron-neutrino coupling constants. A window for this coefficient h, 2 x 10-5 ≤ h ≤ 3 x 10-4, is excluded. Effects on this bound due to interactions not included in the model Lagrangian are also discussed. A novel matter-induced neutrino decay into majorons is described. The decay rate and spectrum are presented in some detail. The significance of this process and its relation with other matter-induced effects are elucidated. Some related remarks are also made about neutrino decay in vacuum. A new Majoron model with very interesting properties is proposed and analyzed. The model has a low-lying symmetry breaking scale, but partly as a result of an unusual symmetry breaking pattern, there is no hierarchy problem and all Higgs particles are heavy. The couplings of the majoron with other particles are suppressed and all the phenomenological bounds, including the constraint from the recent Z0 decay width measurements, can be easily satisfied