Bounds on new Majoron models from the Heidelberg-Moscow experiment.

Abstract

In recent years several new Majoron models were invented to avoid the shortcomings of the ordinary models while leading to observable decay rates in double $\ensuremath{\beta}$ experiments. We give the first experimental half-life bounds on double $\ensuremath{\beta}$ decays with new Majoron emission and derive bounds on the effective neutrino-Majoron couplings from the data of the $^{76}\mathrm{Ge}$ Heidelberg-Moscow experiment. While stringent half-life limits for all decay modes and the coupling constants of the ordinary models were obtained, small matrix elements and phase space integrals result in much weaker limits on the effective coupling constants of the new Majoron models.