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preprints:2008:ttp08-42 [2016/03/17 11:03] (current)
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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]] ​  | 
 +| |