Speaker
Description
The systematic combination of perturbative QCD with parton-shower resummation is achieved at NLO by a small, but growing, number of 'NLO matching' methods.
Among them, the KrkNLO method is unique in exploiting a modification of the PDF factorisation scheme, from the conventional $\overline{\mathrm{MS}}$ scheme, to a scheme (the 'Krk' scheme) in which the NLO corrections can be applied as a simple multiplicative reweight. This is positive by construction, since it does not use subtraction, and unlike other methods has no dependence on an unphysical choice of shower-scale or suppression factor.
We summarise the KrkNLO method, its recent implementation for general colour-singlet processes in Herwig 7, and present results for LHC processes involving the production of massive and massless vector bosons. We will summarise the results of a systematic comparison with MC@NLO, and also review the properties of the Krk scheme among other factorisation schemes proposed as alternatives to $\overline{\mathrm{MS}}$, including their positivity.
