Higgs Decay into Two Photons, Revisited

TL;DR

This paper presents a finite one-loop calculation of the Higgs decay into two photons, avoiding divergences and dimensional regularization, and clarifies differences with previous results.

Contribution

It provides a straightforward, divergence-free calculation of the Higgs to two photons decay amplitude in the unitary gauge, contrasting prior regularization-based methods.

Findings

The calculation is finite and gauge-invariant.

Results differ from earlier dimensional regularization approaches.

The method satisfies the decoupling theorem for large Higgs mass.

Abstract

The one-loop calculation of the amplitude for the Higgs decay H-->\gamma\gamma\ due to virtual W's in the unitary gauge is presented. As the Higgs does not directly couple to the massless photons, the one-loop amplitude is finite. The calculation is performed in a straightforward way, without encountering divergences. In particular, artifacts like dimensional regularization are avoided. This is achieved by judiciously routing the external momenta through the loop and by combining the integrands of the amplitudes before carrying out the integration over the loop momentum. The present result satisfies the decoupling theorem for infinite Higgs mass, and is thus different from the earlier results obtained in the \xi=1 gauge using dimensional regularization. The difference between the results is traced to the use of dimensional regularization.