Short-range neutrinoless double beta decay mechanisms

Abstract

Neutrinoless double beta decay can significantly help to shed light on the issue of nonzero neutrino mass, as the observation of this lepton-number-violating process would imply that neutrinos are Majorana particles. However, the underlying interaction does not have to be as simple as the standard neutrino mass mechanism. The entire variety of neutrinoless double beta decay mechanisms can be approached effectively. In this work, we focus on a theoretical description of short-range effective contributions to neutrinoless double beta decay, which are equivalent to nine-dimensional effective operators incorporating the appropriate field content. We give a detailed derivation of the nuclear matrix elements and phase-space factors corresponding to individual terms of the effective Lagrangian. Using these, we provide general formulas for the neutrinoless double beta decay half-life and angular correlation of the outgoing electrons.