Nonperturbative study of the electroweak phase transition in the real scalar singlet extended Standard Model

TL;DR

This study uses nonperturbative lattice methods to analyze the electroweak phase transition in a scalar singlet extended Standard Model, revealing conditions for first-order transitions and validating perturbative approaches.

Contribution

First nonperturbative lattice analysis of the electroweak phase transition in the scalar singlet extended Standard Model, comparing with perturbative results across parameter regimes.

Findings

Transition is crossover at small mixing angles in heavy scalar regime.

Transition becomes first order at large mixing angles.

Two-loop perturbation theory agrees with lattice results for strongly first order transitions.

Abstract

We perform a nonperturbative lattice study of the electroweak phase transition in the real singlet scalar extension of the Standard Model.We consider both the heavy and light singlet-like scalar regimes at non-zero singlet-doublet mixing angle. After reviewing features of the lattice method relevant for phase transition studies, we analyze the dependence of phase transition thermodynamics on phenomenologically relevant parameters. In the heavy singlet-like scalar regime, we find that the transition is crossover for small doublet-singlet mixing angles, despite the presence of an energy barrier in the tree-level potential. The transition becomes first order for sufficiently large mixing angles. We find two-loop perturbation theory to agree closely with the lattice results for all thermodynamical quantities considered here (critical temperature, order parameter discontinuity, latent heat) when the transition is strongly first order. For the light singlet-like scalar regime relevant to exotic Higgs decays, we update previous one-loop perturbative results using the two-loop loop dimensionally reduced effective field theory and assess the nature of the transition with lattice simulations at set of benchmark parameter points. For fixed singlet-like scalar mass the transition becomes crossover when the magnitude of the Higgs-singlet portal coupling is small. We perform our simulations in the high-temperature effective theory, which we briefly review, and present analytic expressions for the relevant lattice-continuum relations.