Non-Standard Neutrinoless Double Beta Decay and Its Implications

by Lukáš Gráf (UCL)

Thursday 7 Dec 2017, 14:00 → 15:00 Europe/London

OC218 (IPPP)

In my talk I will focus on the effective approach to lepton number violation and implications of potential future observation of lepton number violating (LNV) processes, primarily of neutrinoless double beta (0vbb) decay. This rare nuclear process can be triggered by a number of mechanisms that can be described at low-energy by dimension-9 0vbb effective operators. The corresponding microscopic description including a thorough calculation of relevant nuclear matrix elements and phase-space factors allows for the estimation of the associated effective couplings and it can also help to pinpoint the dominant mechanism triggering 0vbb decay. The low-energy 0vbb operators can be encoded in terms of Standard Model effective operators violating lepton number by two units. Consequently, it is possible to draw an interplay between lepton number violation at high and low energies. Specifically, the contribution of the SM effective operators to the rate of 0vbb decay can be correlated with the washout of lepton number induced by the same operators in the early universe. As I will show, the observation of a non-standard contribution to 0vbb decay, i.e. not induced by the standard mass mechanism of light neutrino exchange, would in fact correspond to an efficient washout of lepton number above the electroweak scale for many SM effective operators up to mass dimension 11.