The Electroweak Phase Transition in the Inert Doublet Model

TL;DR

This paper investigates the potential for a strong first-order electroweak phase transition within the Inert Doublet Model, emphasizing the role of dark matter candidates and the impact of experimental constraints on model viability.

Contribution

It improves the treatment of the finite-temperature effective potential and explores how adjusting Higgs masses can enhance the phase transition strength in the IDM.

Findings

A strong first-order phase transition is generally achievable in the IDM.

The Higgs funnel regime is necessary for compatibility with dark matter and collider constraints.

Adjusting inert Higgs masses can significantly strengthen the electroweak phase transition.

Abstract

We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.