  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.
