A resonance-aware MC@NLO QCD+EW-matched calculation of lepton-pair production

Abstract

As we approach HL-LHC, there is a growing need for increased precision in theoretical predictions so that meaningful comparisons with experimental data can be made. It is no longer sufficient to include only QCD higher-order corrections, with EW effects becoming increasingly important. Even at hadron colliders, QED radiation provides large corrections to some observables. In this paper, we present the first automated matching of NLO QCD+EW to an interleaved QCD+QED parton shower using the MC@NLO matching method in the Catani-Seymour dipole formalism. When considering such a matched parton shower, the presence of resonances can lead to spurious higher order terms, originating in the recoil assignment, within the standard dipole construction. We therefore develop a resonance-aware modification to the MC@NLO algorithm that can be applied to QCD- and QED-singlet resonances. We validate our interleaved matching and its resonance-aware modification against fixed-order NLO QCD+EW and pure MC@NLO QCD combined with YFS resummation. Finally, we present resonance-aware MC@NLO QCD+EW predictions for Drell-Yan lepton pair production, a vital precision process at hadron colliders.