Theoretical implications of 0νββ decay measurements

Abstract

Lower limits on the half-life of neutrinoless double beta (0νββ) decay are usually interpreted as an upper limit on the effective Majorana neutrino mass. However, from a theoretical point of view 0νββ decay is an effective dimension-9 (ΔL = 2) operator, 𝒪0νββ, for which the mass mechanism is only one possible realization. Any new physics model, which allows for lepton number violation (LNV), will contribute to the 0νββ decay amplitude. Here, after some preliminaries, I will discuss the general decomposition of 𝒪0νββ. Most “exotic” contributions to 0νββ decay are of the so-called “short-range” type, i.e. involve heavy, electrically charged (and/or coloured) particles. Thus, current and future LHC data will put these exotic contributions to the test and either discover signals for LNV or rule out most cases as possible explanations of a hypothetical future signal of 0νββ decay.