Single Higgs-boson production through γγ scattering within the general 2HDM

The production of a single neutral Higgs boson h through (loop-induced) γγ collisions is explored in the context of the linear colliders within the general Two-Higgs-Doublet Model (2HDM). Two different mechanisms are analyzed: on the one hand, the scattering γγ→h of two real photons in a γγ collider; on the other, the more traditional mechanism of virtual photon fusion, e+e−→e+e−γ∗γ∗→e+e−+h. Owing to the peculiar properties of the Higgs boson self-interactions within the general 2HDM, we find that the overall production rates can be boosted up significantly, provided the charged Higgs mass is not too heavy. For example, if MH±≳100 GeV and, in addition, Mh0 falls in the ballpark of the LEP bound on the SM Higgs mass up to a few hundred GeV, the cross-sections may typically render 〈σγγ→h〉∼0.1-1 pb and σ(e+e−→e+e−h0)≲0.01 pb - in both cases well above the SM prediction. Although for MH±>300 GeV the rates become virtually insensitive to the Higgs boson self-couplings, a significant tail of non-SM effects produced by the combined contribution of the Yukawa couplings and gauge bosons could still reveal a smoking gun.