A complete O(alpha_S²) calculation of the signal-background interference for the Higgs diphoton decay channel

We present the full ${\cal O}(\as^2)$ computation of the interference effects between the Higgs diphoton signal and the continuum background at the LHC. While the main contribution to the interference originates on the $gg$ partonic subprocess, we find that the corrections from the $qg$ and $q\bar{q}$ channels amount up to 35% of it. We discuss the effect of these new subprocesses in the shift of the diphoton invariant mass peak recently reported by S. Martin in Ref.\cite{Martin:2012xc}.