Neutrinoless Double Beta Decay and the Baryon Asymmetry of the Universe

TL;DR

This paper explores how observing neutrinoless double beta decay could indicate lepton number violation in the early universe, potentially affecting baryogenesis mechanisms and the matter-antimatter asymmetry.

Contribution

It links neutrinoless double beta decay mechanisms to lepton number washout in the early universe, highlighting implications for high-scale baryogenesis.

Findings

Non-standard decay contributions imply efficient lepton number washout.

Many operators up to dimension 11 can erase lepton asymmetry.

Implications for the viability of high-scale baryogenesis mechanisms.

Abstract

We discuss the impact of the observation of neutrinoless double beta decay on the washout of lepton number in the early universe. Neutrinoless double beta decay can be triggered by a large number of mechanisms that can be encoded in terms of Standard Model effective operators which violate lepton number by two units. We calculate the contribution of such operators to the rate of neutrinoless double beta decay and correlate it with the washout of lepton number induced by the same operators in the early universe. We find that the observation of a non-standard contribution to neutrinoless double beta decay, i.e. not induced by the standard mass mechanism of light neutrino exchange, would correspond to an efficient washout of lepton number above the electroweak scale for many operators up to mass dimension 11. Combined with Standard Model sphaleron transitions, this would render many baryogenesis mechanisms at higher scales ineffective.