Leptogenesis in automatic Nelson-Barr models

TL;DR

This paper demonstrates that automatic Nelson-Barr models with new chiral fermions can simultaneously address the strong CP problem and produce the observed baryon asymmetry through high-scale leptogenesis, linking CP violation origins.

Contribution

It introduces a novel class of models where a single spontaneous symmetry-breaking scale accounts for quark and lepton CP phases, enabling successful leptogenesis without compromising the strong CP solution.

Findings

Viable parameter space for leptogenesis identified

Correlation between baryon asymmetry and QCD vacuum angle shift predicted

Most parameter space accessible to current and future nucleon EDM experiments

Abstract

In this study, we numerically show that automatic Nelson-Barr models with new chiral fermions can simultaneously solve the strong CP problem and generate the observed baryon asymmetry via high-scale leptogenesis. In these models, all CP violation arises from a single spontaneous symmetry-breaking scale, linking the origin of quark and lepton CP phases. Using conservative assumptions and minimal dynamics, we identify a viable parameter window where successful leptogenesis occurs without spoiling the quality of the strong CP solution. Models with vector-like fermions face tension within this leptogenesis scenario. A key prediction is a correlation between the baryon asymmetry and the induced QCD vacuum angle shift. Remarkably, we find that the majority of the available parameter space is within reach of current and future nucleon EDM experiments.