New constraints on extended Higgs sectors from the trilinear Higgs coupling

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.