Bulg. J. Phys. vol.42 no.3 (2015), pp. 296-304



Once More on the W-Loop Contribution to the Higgs Decay into Two Photons

E. Christova, I. Todorov
Institute of Nuclear Research and Nuclear Energy, Bulgarian Acadademy of Sciences, 72 Tsarigradsko Chaussee, BG-1784 Sofia, Bulgaria
Abstract. The imaginary part of the Feynman amplitude of the W-loop contribution to the Higgs decay into two gammas (viewed as a function of the square of the off shell Higgs momentum) is finite and unambiguous. It is presented as the product of an invariant amplitude times a bilinear in the components of the (on shell) photon momenta factor which takes the Ward identity into account. The unsubtracted dispersion integral of is convergent and reproduces the amplitude computed by R. Gastmans, S.L. Wu and T.T. Wu [6]. In particular, the decoupling theorem, criticized as an unjustified assumption in a subsequent paper [15], is obtained as a corollary. By contrast with the currently used value (computed in [14]) our calculation provides a smaller Higgs decay rate into 2 photons than the corrently observed. If accepted as a true prediction of the Standard Model, it would be a first indication for the need of a New Physics.

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