Spontaneous thermal Leptogenesis via Majoron oscillation

TL;DR

This paper proposes a new spontaneous Leptogenesis model where the Majoron field's motion in thermal equilibrium generates lepton asymmetry without requiring out-of-equilibrium decays, linking neutrino masses to baryon asymmetry.

Contribution

It introduces a spontaneous Leptogenesis mechanism involving Majoron oscillation in thermal equilibrium, bypassing the need for CP-violating decays of heavy neutrinos.

Findings

Lepton asymmetry can be generated in thermal equilibrium via Majoron dynamics.

Predicted neutrino mass ranges compatible with observed baryon asymmetry.

Effective mass for neutrinoless double beta decay is constrained by the model.

Abstract

A novel model of spontaneous Leptogenesis is investigated, where it takes place in the thermal equilibrium due to a background Nambu-Goldstone field in motion. In particular, we identify the Nambu-Goldstone field to be the Majoron which associates with spontaneous breakdown of (discrete) $B-L$ symmetry. In this scenario sufficient lepton number asymmetry is generated in primordial thermal bath without having $CP$-violating out-of-equilibrium decay of the heavy right-handed Majorana neutrinos. To obtain the observed baryon asymmetry, the neutrino masses are predicted in certain ranges, which can be translated into the effective mass of the neutrinoless double beta decay.