Electroweak-like Baryogenesis with New Chiral Matter

TL;DR

This paper introduces a new baryogenesis mechanism involving a phase transition above the electroweak scale, leveraging extended gauge symmetry and chiral fermions to generate the observed matter-antimatter asymmetry.

Contribution

It presents a novel baryogenesis framework with a strong first-order phase transition and new CP violation, avoiding suppression by Yukawa couplings, and links to dark matter and gravitational wave signals.

Findings

The model achieves sufficient baryon asymmetry with a strong first-order phase transition.

It predicts new particles detectable at colliders.

It suggests gravitational wave signatures from the phase transition.

Abstract

We propose a framework where a phase transition associated with a gauge symmetry breaking that occurs (not far) above the electroweak scale sets a stage for baryogenesis similar to the electroweak baryogenesis in the Standard Model. A concrete realization utilizes the breaking of $SU(2)_R \times U(1)_X \rightarrow U(1)_Y$. New chiral fermions charged under the extended gauge symmetry have nonzero lepton numbers, which makes the $B-L$ symmetry anomalous. The new lepton sector contains a large flavor-dependent CP violation, similar to the Cabibbo-Kobayashi-Maskawa phase, without inducing sizable electric dipole moments of the Standard Model particles. A bubble wall dynamics associated with the first-order phase transition and $SU(2)_R$ sphaleron processes generate a lepton asymmetry, which is transferred into a baryon asymmetry via the ordinary electroweak sphaleron process. Unlike the Standard Model electroweak baryogenesis, the new phase transition can be of the strong first order and the new CP violation is not significantly suppressed by Yukawa couplings, so that the observed asymmetry can be produced. The model can be probed by collider searches for new particles and the observation of gravitational waves. One of the new leptons becomes a dark matter candidate. The model can be also embedded into a left-right symmetric theory to solve the strong CP problem.