Higgs vacua with potential barriers

TL;DR

This paper investigates Higgs vacua with potential barriers in models with extra singlet scalars, analyzing the effective potential and phase transitions, and explores experimental signatures at colliders.

Contribution

It provides a detailed two-loop analysis of the effective potential in singlet scalar models, demonstrating the viability of strong first-order phase transitions with controlled quantum corrections.

Findings

Two-loop effects are well-behaved even with large couplings.

Strong first-order phase transitions are achievable in these models.

Deviations in Higgs couplings could be detected at linear colliders.

Abstract

Scenarios in which the Higgs vacuum arises radiatively and is separated from the origin by a potential barrier at zero temperature are known to be attainable in models with extra singlet scalars, which in the limit of zero barrier height give rise to Coleman-Weinberg realizations of electroweak symmetry breaking. However, this requires large values of Higgs-portal couplings or a large number N of singlets. This is quantified in detail by considering, for varying N, the full two-loop effective potential at zero temperature, as well as finite temperature effects including the dominant two-loop corrections due to the singlets. Despite the large couplings, two-loop effects near the electroweak scale are under control, and actually better behaved in models with larger couplings yet fewer singlets. Strong first-order phase transitions are guaranteed even in the Coleman-Weinberg scenarios. Cubic Higgs couplings and Higgs associated-production cross sections exhibit deviations from the Standard Model predictions which could be probed at a linear collider.