Higgs decay into two photons in a warped extra dimension

A detailed five-dimensional calculation of the Higgs-boson decay into two photons is performed in both the minimal and the custodially protected Randall–Sundrum (RS) model, where the Standard Model (SM) fields propagate in the bulk and the scalar sector lives on or near the IR brane. It is explicitly shown that the Rξ gauge invariance of the sum of diagrams involving bosonic fields in the SM also applies to the case of these RS scenarios. An exact expression for the h→γγ amplitude in terms of the five-dimensional (5D) gauge-boson and fermion propagators is presented, which includes the full dependence on the Higgs-boson mass. Closed expressions for the 5D W -boson propagators in the minimal and the custodial RS model are derived, which are valid to all orders in v2/MKK2 . In contrast to the fermion case, the result for the bosonic contributions to the h→γγ amplitude is insensitive to the details of the localization of the Higgs profile on or near the IR brane. The various RS predictions for the rate of the pp→h→γγ process are compared with the latest LHC data, and exclusion regions for the RS model parameters are derived