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+ | ====== TTP08-42 NNLO Computational Techniques: the Case $H \to \gamma\gamma,gg$ ====== | ||

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+ | <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]] | | ||

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