# Differences

This shows you the differences between two versions of the page.

 — preprints:2008:ttp08-42 [2016/03/17 11:03] (current) Line 1: Line 1: + ====== 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. + ​ + |**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]] ​  | + | |