Leptogenesis from a Phase Transition in a Dynamical Vacuum

TL;DR

This paper proposes a novel leptogenesis mechanism triggered by a phase transition involving a scalar field coupled to right-handed neutrinos, producing the observed baryon asymmetry with testable predictions.

Contribution

It introduces a temperature-dependent mass mechanism for right-handed neutrinos via a scalar field, linking early Universe phase transitions to leptogenesis and primordial lepton asymmetry.

Findings

Leptogenesis can occur near a phase transition temperature $T_*$ with sub-GeV RHN masses.

The model predicts a primordial lepton asymmetry correlated with early Universe conditions.

The scenario is testable through its implications for baryon asymmetry and helium abundance measurements.

Abstract

We show that a phase transition may take place in the early Universe at a temperature $T_*$ via a Standard Model singlet scalar field which happens to couple to right handed neutrinos (RHN) resulting a temperature dependent mass for them that finally relaxes to a constant value after electroweak phase transition (EWPT). As a result, a requisite amount of lepton asymmetry can be produced at a temperature close to $T_*$ satisfying the observed baryon asymmetry of the Universe via sphaleron process even when the zero temperature masses of the RHNs fall in sub GeV regime providing a testable scenario for leptogenesis. Interestingly, the framework is also capable of predicting a primordial lepton asymmetry (generated at a temperature below the EWPT), as hinted by helium abundance measuring experiments, bearing a correlation with early phase of leptogenesis.