On the validity of perturbative studies of the electroweak phase transition in the Two Higgs Doublet model

Kimmo Kainulainen,Kari Rummukainen,Venus Keus,Tuomas V. I. Tenkanen,Ville Vaskonen,Lauri Niemi

doi:10.1007/jhep06(2019)075

Abstract

Making use of a dimensionally-reduced effective theory at high temperature, we perform a nonperturbative study of the electroweak phase transition in the Two Higgs Doublet model. We focus on two phenomenologically allowed points in the parameter space, carrying out dynamical lattice simulations to determine the equilibrium properties of the transition. We discuss the shortcomings of conventional perturbative approaches based on the resummed effective potential — regarding the insufficient handling of infrared resummation but also the need to account for corrections beyond 1-loop order in the presence of large scalar couplings — and demonstrate that greater accuracy can be achieved with perturbative methods within the effective theory. We find that in the presence of very large scalar couplings, strong phase transitions cannot be reliably studied with any of the methods.

Highlights

Transition (EWPT) at a temperature T ∼ 100 GeV
We discuss the shortcomings of conventional perturbative approaches based on the resummed effective potential — regarding the insufficient handling of infrared resummation and the need to account for corrections beyond 1-loop order in the presence of large scalar couplings — and demonstrate that greater accuracy can be achieved with perturbative methods within the effective theory
Nonperturbative lattice studies in the SM have revealed that the Higgs boson is too heavy to lead to a large potential barrier between the symmetric and broken phases, and the electroweak symmetry breaking in the SM is a smooth crossover [11,12,13,14,15]

Summary

Introduction

Transition (EWPT) at a temperature T ∼ 100 GeV. the SM contains all the required ingredients for EWBG [3,4,5], it is unable to explain the observed baryon excess due to its insufficient amount of CP violation [6,7,8,9,10] and the lack of a first-order EWPT. A common feature of BSM models with strongly first-order EWPT is that the relevant new fields can be light and dynamically active during the phase transition This setup potentially leads to a multi-step transition with a tree-level potential barrier between the intermediate minimum and the final Higgs phase [28,29,30,31,32,33]. In the context of the EWPT, variations of 2HDMs have been considered where the phase transition is analyzed using the perturbative effective potential [36,37,38,39,40,41,42,43,44,45] In these works, a strongly first order EWPT is achieved through scalar couplings of O(1) or larger, which raises concerns of the performance of perturbation theory already at zero temperature. The EFT is effectively three dimensional (hereafter 3d EFT), simplifying both perturbative and nonperturbative computations.

Objectives

Methods

Findings

Conclusion