Strong first order electroweak phase transition in 2HDM confronting future Z & Higgs factories

TL;DR

This paper investigates the conditions for a strong first order electroweak phase transition in 2HDM models, constraining Higgs spectrum and exploring detection prospects at future precision colliders.

Contribution

It provides a detailed analysis of how SFOEWPT constrains the Higgs spectrum in 2HDM and assesses the potential for future colliders to probe these conditions.

Findings

SFOEWPT favors heavy Higgs masses below 1 TeV.

Analytical understanding via high temperature expansion supports numerical results.

Future Higgs and Z factories can test SFOEWPT-related parameter space.

Abstract

The electroweak phase transition can be made first order by extending the Standard Model (SM) Higgs sector with extra scalars. The same new physics can explain the matter-antimatter asymmetry of the universe by supplying an extra source of CP violation and sphaleron processes. In this paper we study the existence of a strong first order electroweak phase transition (SFOEWPT) in the type-I and type-II two Higgs doublet models (2HDM). We focus on how the SFOEWPT requirement constraints the spectrum of non-SM Higgs. Through a parameter space scan, we find that SFOEWPT suggests upper limits on the masses of heavy Higgs $m_{A/H/H^\pm}$, which is less than 1 TeV. High temperature expansion and Higgs vacuum uplifting is used for an analytical understanding of our results. We also study the probe ability on SFOEWPT from Higgs and $Z$-pole precision measurements at the one-loop level at future Higgs & $Z$ factories. And together with theoretical constraints, sizeable loop corrections require $m_A \approx m_{H^\pm} > m_H$ to meet SFOEWPT condition in Type-II 2HDM.