On the two-loop BSM corrections to $h⟶\gamma \gamma$ in the aligned THDM

Abstract

We compute the two-loop BSM contributions to the $h⟶\gamma \gamma$ decay width in the aligned THDM. We adopt the simplifying assumptions of vanishing EW gauge couplings and vanishing mass of the SM-like Higgs boson, which allow us to exploit a low-energy theorem connecting the $h\gamma \gamma$ amplitude to the derivative of the photon self-energy w.r.t. the Higgs field. We briefly discuss the numerical impact of the newly-computed contributions, showing that they may be required for a precise determination of $\Gamma [h\to \gamma \gamma ]$ in scenarios where the quartic Higgs couplings are large.

Comments: 25 pages, 2 PDF figures; v2: discussion of decoupling added in section 3, version to appear in EPJC