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Study of perturbative QCD predictions at next-to-leading order and beyond for \pp -> H -> gamma gamma + X

We study predictions from perturbative Quantum Chromodynamics (QCD) for the process pp -> H -> gamma gamma + X. In particular, we compare fully differential calculations at next-to-leading (NLO) and next-to-next-to-leading order (NNLO) in the strong coupling constant to the results obtained with the MC@NLO Monte Carlo (MC) generator, which combines QCD matrix elements at NLO with a parton shower algorithm. Estimates for the systematic uncertainties in the various predictions due to the choice of the renormalization scale and the parton distribution functions are given for the inclusive and accepted cross sections and for the corresponding acceptance corrections, obtained after applying standard selection and acceptance cuts. Furthermore, we compare the distributions for the Higgs signal to those for the irreducible two-photon background, obtained with a NLO MC simulation.