Neutrinoless double beta decay: 2015 review

Abstract

The discovery of neutrino masses through the observation of oscillations boosted the importance of neutrinoless double beta decay ($0νββ$). In this paper, we review the main features of this process, underlining its key role both from the experimental and theoretical point of view. In particular, we contextualize the $0νββ$ in the panorama of lepton-number violating processes, also assessing some possible particle physics mechanisms mediating the process. Since the $0νββ$ existence is correlated with neutrino masses, we also review the state-of-art of the theoretical understanding of neutrino masses. In the final part, the status of current $0νββ$ experiments is presented and the prospects for the future hunt for $0νββ$ are discussed. Also, experimental data coming from cosmological surveys are considered and their impact on $0νββ$ expectations is examined.