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

TL;DR

This paper calculates two-loop beyond Standard Model corrections to the Higgs to diphoton decay in the aligned Two-Higgs-Doublet Model, highlighting their importance for precise theoretical predictions.

Contribution

It introduces a novel two-loop calculation of BSM effects on Higgs decay in the aligned THDM using a low-energy theorem approach.

Findings

Two-loop BSM contributions can significantly affect the Higgs to diphoton decay width.

The results are relevant for scenarios with large quartic Higgs couplings.

The approach simplifies calculations by assuming vanishing electroweak gauge couplings and Higgs mass.

Abstract

We compute the two-loop BSM contributions to the $h\longrightarrow \gamma\gamma$ 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 $\Gamma[h\rightarrow \gamma \gamma]$ in scenarios where the quartic Higgs couplings are large.