Neutrinoless double beta decay and the baryon asymmetry of the Universe

Frank F Deppisch,Wei-Chih Huang,Lukas Graf,Julia Harz

doi:10.1103/physrevd.98.055029

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.

Highlights

The dynamics of the standard model (SM) is determined by its gauge symmetry and chiral structure
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 find that the observation of a nonstandard 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

Summary

Introduction

The dynamics of the standard model (SM) is determined by its gauge symmetry and chiral structure. Does the group SUð3ÞC × SUð2ÞL × Uð1ÞY explain the interactions we observe in nature, its breaking provides masses to the charged fermions via the Higgs mechanism. The discovery of the Higgs boson at the Large Hadron Collider (LHC) [1,2] has put us into the position to probe and verify this mass mechanism in the SM. Being only left-handed, neutrinos cannot acquire a socalled Dirac mass like the other SM fermions. While oscillations cannot probe the absolute masses of neutrinos, they point to mass scales of order 10−2 eV to 5 × 10−2 eV corresponding to the solar and atmospheric oscillation lengths, respectively.

Objectives

Results

Conclusion