First-order phase transitions in Twin Higgs models

TL;DR

This paper investigates conditions under which strong first-order phase transitions can occur in Twin Higgs models, exploring their potential to produce detectable gravitational waves and contribute to baryogenesis.

Contribution

It identifies new classes of Twin Higgs models with strong FOPTs driven by specific Z2 symmetry breaking mechanisms, including supersymmetric extensions.

Findings

FOPTs can occur with appropriate Z2 symmetry breaking.

Gravitational wave signals may be detectable by future experiments.

Models can potentially explain the SM baryon asymmetry.

Abstract

We revisit phase transitions in Twin Higgs (TH) models. We show that strong first-order phase transitions (FOPTs) can occur provided that appropriate source of $\mathbb{Z}_2$ symmetry breaking between the twin and Standard Model (SM) sectors is present. We found FOPTs in two classes of models. First: with hard $\mathbb{Z}_2$ breaking in the scalar potential allowing for FOPT. Second: with $\mathbb{Z}_2$ broken by enhanced Yukawa couplings of twin leptons. We also considered supersymmetric UV completion of the second scenario with light sleptons. The signal of gravitational waves produced during these phase transitions is typically small but can be close to the reach of AEDGE and Einstein Telescope in the case of the FOPT induced by light twin sleptons. Our results open a way to generate SM baryon asymmetry in TH models.