KrkNLO matching for colour-singlet processes

Matched calculations combining perturbative QCD with parton showers are an indispensable tool for LHC physics. Two methods for NLO matching are in widespread use: Mc@Nlo and Powheg. We describe an alternative, KrkNLO, reformulated to be easily applicable to any colour-singlet process. The primary distinguishing characteristic of KrkNLO is its use of an alternative factorisation scheme, the ‘Krk’ scheme, to achieve NLO accuracy. We describe the general implementation of KrkNLO in Herwig 7, using diphoton production as a test process. We systematically compare its predictions to those produced by Mc@Nlo with several different choices of shower scale, both truncated to one-emission and with the shower running to completion, and to Atlas data from LHC Run 2.