Two-loop corrections to $gg \to \gamma \gamma$
  An overview of the calculation of the two-loop helicity amplitudes for scattering of two gluons into two photons is presented. These matrix elements enter into the recent improved calculation of the QCD background to Higgs boson decay into a pair of photons, which is the preferred search mode at the LHC for the case of a light Higgs boson. 
Z. Bern (UCLA), A. De Freitas (DESY, Zeuthen), L. Dixon (SLAC)