Electroweak Phase Transition and Baryogenesis in Composite Higgs Models

TL;DR

This paper investigates the electroweak phase transition in composite Higgs models, demonstrating it can be first-order and suitable for baryogenesis, with detailed analysis of CP violation mechanisms and parameter space.

Contribution

It provides a comprehensive analysis of the electroweak phase transition and baryogenesis in composite Higgs models, including a numerical study of tunneling with varying Yukawa couplings.

Findings

Electroweak phase transition can be first-order in composite Higgs models.

Varying charm Yukawa coupling can enable successful baryogenesis.

Light dilaton region is favored for baryogenesis while satisfying experimental bounds.

Abstract

We present a comprehensive study of the electroweak phase transition in composite Higgs models, where the Higgs arises from a new, strongly-coupled sector which confines near the TeV scale. This work extends our study in Ref. [1]. We describe the confinement phase transition in terms of the dilaton, the pseudo-Nambu-Goldstone boson of broken conformal invariance of the composite Higgs sector. From the analysis of the joint Higgs-dilaton potential we conclude that in this scenario the electroweak phase transition can naturally be first-order, allowing for electroweak baryogenesis. We then extensively discuss possible options to generate a sufficient amount of CP violation - another key ingredient of baryogenesis - from quark Yukawa couplings which vary during the phase transition. For one such an option, with a varying charm quark Yukawa coupling, we perform a full numerical analysis of tunnelling in the Higgs-dilaton potential and determine regions of parameter space which allow for successful baryogenesis. This scenario singles out the light dilaton region while satisfying all experimental bounds. We discuss future tests. Our results bring new opportunities and strong motivations for electroweak baryogenesis.