Leptogenesis triggered by a first-order phase transition

TL;DR

This paper introduces a novel leptogenesis mechanism triggered by a first-order phase transition, where massless right-handed neutrinos gain mass in bubble walls, generating lepton asymmetry without washout, and explores its realization in an extended B-L model with detectable gravitational waves.

Contribution

It proposes a new leptogenesis scenario driven by a first-order phase transition with massless to massive neutrinos, avoiding washout effects, and connects it to gravitational wave signals.

Findings

The mechanism produces sufficient baryon asymmetry.

Gravitational waves from B-L breaking could be observed.

The model naturally explains neutrino mass generation.

Abstract

We propose a new scenario of leptogenesis, which is triggered by a first-order phase transition (FOPT). The right-handed neutrinos (RHNs) are massless in the old vacuum, while they acquire a mass in the new vacuum bubbles, and the mass gap is huge compared with the FOPT temperature. The ultra-relativistic bubble walls sweep the RHNs into the bubbles, where the RHNs experience fast decay and generate the lepton asymmetry, which is further converted to the baryon asymmetry of the Universe (BAU). Since the RHNs are out of equilibrium inside the bubble, the generated BAU does not suffer from the thermal bath washout. We first discuss the general feature of such a FOPT leptogenesis mechanism, and then realize it in an extended $B-L$ model. The gravitational waves from $U(1)_{B-L}$ breaking could be detected at the future interferometers.