Abstract
An important task at future colliders is the measurement of the triple Higgs coupling. Depending on its size relative to the Standard Model (SM) value, certain collider options result in a higher experimental accuracy. Within the framework of Two Higgs Doublet Models (2HDM) types I and II we investigate the allowed ranges for all triple Higgs couplings involving at least one light, SM-like Higgs boson. We take into account theoretical constraints (unitarity, stability), experimental constraints from direct Higgs-boson searches, measurements of the SM-like Higgs-boson properties, flavor observables and electroweak precision data. We find that the SM-type triple Higgs coupling w.r.t. its SM value, lambda _{hhh}/lambda _{mathrm {SM}}, can range between sim -0.5 and sim 1.5. Depending on which value is realized, the HL-LHC can compete with, or is clearly inferior to the ILC. We find the coupling lambda _{hhH} between sim -1.5 and sim 1.5. Triple Higgs couplings involving two heavy Higgs bosons, lambda _{hHH}, lambda _{hAA} and lambda _{hH^+H^-} can reach values up to {{mathcal {O}}}(10), roughly independent of the 2HDM type. This can lead to potentially strongly enhanced production of two Higgs-bosons at the HL-LHC or high-energy e^+e^- colliders.
Highlights
The largest relative uncertainties of up to 30% are found close to κλ = 0, whereas the absolute determination exhibits a nearly constant very precise determination of κλ in the interval [−0.5, 1.0]. These results clearly show that the physics potential of a future collider experiment strongly depends on the actual value of λhhh realized in a BSM model
An important task at future colliders is the measurement of the triple Higgs coupling λhhh
Depending on its size relative to the Standard Model (SM) value, certain collider options result in a higher experimental accuracy
Summary
In this paper, focusing on the 2HDM type I and II, we investigate the allowed ranges for all triple Higgs couplings involving at least one light, SM-like Higgs boson. In this work we present a detailed study of the dependence of the triple Higgs couplings on the free parameters of the model Finding a way to obtain large values for m212, still being allowed by experimental data and by the theoretical constraints, turned out to be crucial in the course of this work This constitutes one of the main differences between our present study and previous studies on constraints in the 2HDM, from LHC physics [52–54], EWPO [48,55,56], flavor physics [57] and global fits [51,58–60].
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