NLO Electroweak Corrections to Higgs Decay to Two Photons

The production of the Standard Model Higgs boson in photon-photon collisions represents an interesting mechanism for measuring the partial width Γ(H → γγ) with a 3% accuracy at an upgrade option of the International Linear Collider (see [2] and references therein). Therefore, the computation of radiative corrections to the leading order (LO) decay width [3] has been an active field of research in the last years. QCD corrections to the partial width of an intermediate-mass Higgs boson have been computed at next-to-leading order (NLO) in [4] and at next-to-next-to-leading order (NNLO) in [5]. The NLO result has been extended in [6] to the entire Higgs-mass range. Electroweak NLO corrections have been evaluated in [7] in the large top-mass scenario and in [8] assuming a large Higgs-mass scenario. The two-loop corrections due to light fermions have been derived by the authors of [9], and electroweak effects due to gauge bosons and the top quark have been evaluated through an expansion in the Higgs external momentum in [10]. More recently, all electroweak corrections at NLO have been computed in [11] for a wide range of the Higgs mass, including the region across the W -pair production threshold. It has been shown that the divergent behavior of the amplitude at a two-particle normal threshold can be removed introducing the complex-mass scheme of [12], a program carried out in [13]. Note that we have not addressed the issue of re-summing Coulomb singularities, as performed by the authors of [14]. In Section 2 of this note we review the implementation of the complex-mass scheme in the two-loop computation and the effect on the two-particle threshold region. Next, in Section 3, we discuss the numerical impact of the NLO electroweak corrections on the partial width Γ(H → γγ).