====== TTP08-42 NNLO Computational Techniques: the Case $H \to \gamma\gamma,gg$ ======
 
 
   <hidden TTP08-42  NNLO Computational Techniques: the Case $H \to \gamma\gamma,gg$ > A large set of techniques needed to compute decay rates at the two-loop level are derived an
 d systematized. The main emphasis of the paper is on the two Standard Model decays H -> gamm
 a gamma and H -> g g. The techniques, however, have a much wider range of application: they
 give practical examples of general rules for two-loop renormalization; they introduce simple
  recipes for handling internal unstable particles in two-loop processes; they illustrate sim
 ple procedures for the extraction of collinear logarithms from the amplitude. The latter is
 particularly relevant to show cancellations, e.g. cancellation of collinear divergencies. Fu
 rthermore, the paper deals with the proper treatment of non-enhanced two-loop QCD and electr
 oweak contributions to different physical (pseudo-)observables, showing how they can be tran
 sformed in a way that allows for a stable numerical integration. Numerical results for the t
 wo-loop percentage corrections to H -> gamma gamma, g g are presented and discussed. When ap
 plied to the process pp -> gg + X -> H + X, the results show that the electroweak scaling fa
 ctor for the cross section is between -4 % and + 6 % in the range 100 GeV < Mh < 500 GeV, wi
 thout incongruent large effects around the physical electroweak thresholds, thereby showing
 that only a complete implementation of the computational scheme keeps two-loop corrections u
 nder control.
 </hidden>
|**Stefano Actis, Giampiero Passarino, Christian Sturm, Sandro  Uccirati**  | 
|**  Nucl.Phys.  B811 182-273 2009  **  |
| {{preprints:2008:ttp08-42.pdf|PDF}} {{preprints:2008:ttp08-42.ps|PostScript}} [[http://arxiv.org/abs/0809.3667|arXiv]]   |
| |