MAcNLOPS for ZZ Pair Production at the LHC

Abstract

We present an implementation of the MAcNLOPS matching prescription for $pp \to ZZ$ production in a MadGraph5_aMC@NLO + Pythia8 setup. Starting from a standard MC@NLO event sample, negative H events are removed and compensated by a veto applied to the first shower emission of the S events. The implementation is validated against MC@NLO for radiation-sensitive and inclusive diboson observables. Agreement is found up to a rather small power-suppressed contribution affecting the very low-pT region. The method removes all negative H weights with negligible additional computational cost, while negative S weights are left unchanged, showing that MAcNLOPS is a promising alternative to MC@NLO with a reduced fraction of negative weights.