NLO QCD predictions for $$Z+\gamma $$ Z+γ + jets production with Sherpa

Abstract

Abstract We present precise predictions for prompt photon production in association with a Z boson and jets. They are obtained within the Sherpa framework as a consistently merged inclusive sample. Leptonic decays of the Z boson are fully included in the calculation with all off-shell effects. Virtual matrix elements are provided by OpenLoops and parton-shower effects are simulated with a dipole parton shower. Thanks to the NLO QCD corrections included not only for inclusive $$Z\gamma $$ Zγ production but also for the $$Z\gamma $$ Zγ + 1-jet process we find significantly reduced systematic uncertainties and very good agreement with experimental measurements at $$\sqrt{s}=8\,\mathrm {TeV}$$ s=8TeV . Predictions at $$\sqrt{s}=13\,\mathrm {TeV}$$ s=13TeV are displayed including a study of theoretical uncertainties. In view of an application of these simulations within LHC experiments, we discuss in detail the necessary combination with a simulation of the Z + jets final state. In addition to a corresponding prescription we introduce recommended cross checks to avoid common pitfalls during the overlap removal between the two samples.