Baryogenesis in a Parity Solution to the Strong CP Problem

TL;DR

This paper explores how a parity-based solution to the strong CP problem can enable baryogenesis through a first-order $SU(2)_R$ phase transition, predicting new particles and potential collider signals.

Contribution

It introduces a minimal Higgs model with parity symmetry that addresses the strong CP problem and proposes a novel baryogenesis mechanism via $SU(2)_R$ sphalerons.

Findings

The model allows $SU(2)_R$ sphalerons to generate $B-L$ asymmetry.

Predicted a new hyper-charged fermion linked to $SU(2)_R$ breaking scale.

Potential collider signatures include a singlet scalar and new fermions.

Abstract

Space-time parity can solve the strong CP problem and introduces a spontaneously broken $SU(2)_R$ gauge symmetry. We investigate the possibility of baryogenesis from a first-order $SU(2)_R$ phase transition similar to electroweak baryogenesis. We consider a model with the minimal Higgs content, for which the strong CP problem is indeed solved without introducing extra symmetry beyond parity. Although the parity symmetry seems to forbid the $SU(2)_R$ anomaly of the $B-L$ symmetry, the structure of the fermion masses can allow for the $SU(2)_R$ sphaleron process to produce non-zero $B-L$ asymmetry of Standard Model particles so that the wash out by the $SU(2)_L$ sphaleron process is avoided. The setup predicts a new hyper-charged fermion whose mass is correlated with the $SU(2)_R$ symmetry breaking scale and hence with the $SU(2)_R$ gauge boson mass, and depending on the origin of CP violation, with an electron electric dipole moment. In a setup where CP violation and the first-order phase transition are assisted by a singlet scalar field, the singlet can be searched for at future colliders.