Higgs Decay into Two Photons through the W-boson Loop: No Decoupling in the m_W --> 0 Limit

Abstract

We reanalyze the W-boson loop in the amplitude of the Higgs decay into two photons to show the absence of decoupling in the limit of massless W bosons, m_W --> 0. The Higgs coupling to longitudinal polarizations survive in this limit and generates a nonvanishing contribution in the $H\to \gamma\gamma$ decay. This shows that the recent claim of decoupling by R. Gastmans, S.L. Wu, and T.T. Wu is incorrect, and the old calculations for the two photon decay well known in the literature are valid.