Baryogenesis in a parity solution to the strong CP problem

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.