Thermodynamics of a Two-Step Electroweak Phase Transition.

Lauri Niemi,David J. Weir,Michael J. Ramsey-Musolf,Tuomas V. I. Tenkanen

doi:10.1103/physrevlett.126.171802

Abstract

New field content beyond that of the standard model of particle physics can alter the thermal history of electroweak symmetry breaking in the early Universe. In particular, the symmetry breaking may have occurred through a sequence of successive phase transitions. We study the thermodynamics of such a scenario in a real triplet extension of the standard model, using nonperturbative lattice simulations. Two-step electroweak phase transition is found to occur in a narrow region of allowed parameter space with the second transition always being first order. The first transition into the phase of nonvanishing triplet vacuum expectation value is first order in a non-negligible portion of the two-step parameter space. A comparison with two-loop perturbative calculation is provided and significant discrepancies with the nonperturbative results are identified.

Highlights

New field content beyond that of the standard model of particle physics can alter the thermal history of electroweak symmetry breaking in the early Universe
We study the thermodynamics of such a scenario in a real triplet extension of the standard model, using nonperturbative lattice simulations
Introduction.—In the standard model (SM) of particle physics, electroweak (EW) gauge symmetry is spontaneously broken by the vacuum-expectation value (VEV) of the Higgs field

Summary

Introduction

The first transition into the phase of nonvanishing triplet vacuum expectation value is first order in a non-negligible portion of the two-step parameter space. Introduction.—In the standard model (SM) of particle physics, electroweak (EW) gauge symmetry is spontaneously broken by the vacuum-expectation value (VEV) of the Higgs field. For the physical Higgs mass this transition is a smooth crossover rather than a true phase transition [1,2,3], i.e., there is no distinction between the symmetric and broken “phases.” In many beyond the standard model (BSM) scenarios, the introduction of additional scalar fields can result in a scalar potential having vastly different thermal behavior from that of the SM.

Results

Conclusion