New constraints on extended Higgs sectors from the trilinear Higgs coupling

TL;DR

This paper investigates how measurements of the trilinear Higgs coupling constrain extended Higgs models, especially the Two-Higgs-Doublet Model, by analyzing parameter regions with enhanced couplings and current experimental bounds.

Contribution

It provides the first detailed analysis of the impact of current Higgs coupling measurements on the parameter space of extended Higgs sectors, including two-loop corrections.

Findings

Current experimental bounds exclude large regions with enhanced $bb$ in the 2HDM.

Two-loop corrections are essential for accurate constraints.

Results are applicable to a broad class of extended Higgs models.

Abstract

The trilinear Higgs coupling $\lambda_{hhh}$ is crucial for determining the structure of the Higgs potential and for probing possible effects of physics beyond the Standard Model (SM). Focusing on the Two-Higgs-Doublet Model as a concrete example, we identify parameter regions in which $\lambda_{hhh}$ is significantly enhanced with respect to the SM. Taking into account all relevant corrections up to the two-loop level, we show that already current experimental bounds on $\lambda_{hhh}$ rule out significant parts of the parameter space that would otherwise be unconstrained. We illustrate the interpretation of the results on $\lambda_{hhh}$ for a benchmark scenario. Similar results are expected for wide classes of models with extended Higgs sectors.