# Electroweak phase transition and Higgs phenomenology in the Georgi-Machacek model

## TL;DR

This paper studies the electroweak phase transition in the Georgi-Machacek model, exploring conditions for strong first order transitions and their testability at future colliders, with implications for Higgs phenomenology.

## Contribution

It provides a detailed analysis of the electroweak phase transition in the Georgi-Machacek model, identifying parameter spaces compatible with a strong first order transition and experimental constraints.

## Key findings

- Two-step SFOEWPT can occur with small mixing angles.
- LHC Higgs measurements constrain the parameter space.
- Distinct collider signatures differentiate one-step and two-step SFOEWPT.

## Abstract

In this work, we perform the electroweak phase transition study with the Georgi-Machacek model. We investigate both the one-step and two-step strong first order electroweak phase transition (SFOEWPT). The SFOEWPT viable parameter spaces could be tested by the future 14 TeV LHC, HL-LHC, and ILC. The LHC Higgs signal strength measurements severely bound the SFOEWPT valid parameter spaces, a tinny region of the mixing angle between the neutral fields of the isospin-doublet and isospin-triplet scalars around $\alpha\sim 0$ can allow the two-step SFOEWPT to occur. The triplet vacuum expectation value (VEV) is crucial for both SFOEWPT and related Higgs phenomenology. The two-step SFOEWPT can be distinguished from the one-step SFOEWPT through the triple Higgs coupling searches and the low mass doubly charged Higgs searches at colliders.