Bounds on the coupling of the Majoron to light neutrinos from supernova cooling

Abstract

We explore the role of Majoron (J) emission in the supernova cooling process, as a source of the upper bound on neutrino-Majoron coupling. We show that the strongest upper bound on the coupling to ${\ensuremath{\nu}}_{e}$ comes from the ${\ensuremath{\nu}}_{e}{\ensuremath{\nu}}_{e}\ensuremath{\rightarrow}J$ process in the core of a supernova. We also find bounds on diagonal couplings of the Majoron to ${\ensuremath{\nu}}_{\ensuremath{\mu}(\ensuremath{\tau})}{\ensuremath{\nu}}_{\ensuremath{\mu}(\ensuremath{\tau})}$ and on off-diagonal ${\ensuremath{\nu}}_{e}{\ensuremath{\nu}}_{\ensuremath{\mu}(\ensuremath{\tau})}$ couplings in various regions of the parameter space. We discuss the evaluation of the cross section for four-particle interactions $(\ensuremath{\nu}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\nu}}\mathrm{JJ}$ and $\ensuremath{\nu}\stackrel{\ensuremath{\rightarrow}}{J}\ensuremath{\nu}J).$ We show that these are typically dominated by three-particle subprocesses and do not give new independent constraints.