Effective K-factors: A method to include higher order QCD corrections in parton shower Monte Carlos: the example of H→WW*→2lν

Abstract

In the last years, a large effort has gone into accurate higher order (HO) calculations of the Higgs production and various background cross sections. Many reactions are now known to next-to-leading order (NLO) accuracy. For the dominant Higgs production mechanism, the gluon-gluon fusion gg → H, even the next-to-next-to leading order (NNLO) calculations have been performed. In this production channel, higher order QCD corrections were found to increase the leading order (LO) cross section by a factor of more than 2. Most simulations for the LHC are based on LO parton shower Monte Carlos (e.g. PYTHIA, HERWIG), which do not include these higher order QCD corrections. In order to get more accurate simulations, it is important to take such contributions into account.