QCD ex-machina: KrkNLO method for general colour-singlet processes

by Andrzej Siodmok (Jagiellonian Univ. Krakow and CERN)

Thursday 15 May 2025, 14:00 → 16:00 Europe/Warsaw

Among NLO matching with Parton Shower methods, the KrkNLO method is unique in that it exploits a modification of the PDF factorisation scheme, allowing NLO accuracy to be achieved through a multiplicative reweighting. This gives positive weights by construction since subtraction is not used. Unlike other matching methods, it is not dependent on an unphysical choice of shower scale or suppression factor.
Here, we summarise the recent implementation of the method for general colour-singlet processes in Herwig 7 and present results for LHC processes involving the production of massive and massless vector bosons. We summarise the results of a systematic comparison with MC@NLO and review the properties of the Krk scheme and other proposed factorisation schemes as useful alternatives to MSbar, including their positivity properties.