Double Beta Decay with Vector Majorons

Abstract

We consider the possibility that neutrinoless double beta decay may occur in models with unbroken lepton number via the emission of a massive gauge boson with electron lepton number $-2$. We determine the shape of the $β\,β$ sum energy spectrum as a function of the gauge coupling, independent of model-specific details. We discuss our results in light of the persistent experimental claims that excess events are observed near but below the spectrum endpoint of several elements.