Probing Standard Model-like di-Higgs Production at Photon-Photon Colliders in the I(1+2)HDM Type-I

Abstract

In this paper, pair production of Standard Model (SM)-like Higgs bosons, $hh$, is studied through $γγ$ scattering at future electron-positron colliders, in the framework of the Inert Doublet Model with two Active Doublets, i.e., the I(1+2)HDM for short. The relevance of the process $γγ\to hh$ for such a Beyond the SM (BSM) scenario stems from the fact that it is a one-loop process at lowest order, wherein inert charged states $χ^\pm$ contribute alongside with $W^\pm$, $H^\pm$ and heavy fermions (primarily, bottom and top quarks), crucially, at the same perturbative order. {Given that $χ^\pm/H^\pm$ masses and $hS^+S^-$ ($S^\pm=χ^\pm, H^\pm$) couplings are very mildly constrained,} there exist regions of the parameter space of the I(1+2)HDM where the former can be rather light and the latter rather large. After imposing up-to-date theoretical and experimental constraints on the I(1+2)HDM, it is found that the production rates of such process at future $γγ$ machines can be enhanced up to a factor of $\approx$ $50$ with respect to the SM, significantly exceeding typical yields of conventional 2-Higgs Doublet Models (2HDMs). Further, thanks to the level of control that one can attain at such facilities on the photon kinematics, leading to excellent invariant mass resolution of the incoming photon pairs, we show how it is possible to extract from this process the value of the $χ^\pm$ mass (along that of the active $H^\pm$ states) with high precision, whichever the decays of the $hh$ pair, both with and without beam polarization.