NLO QCD predictions for \(Z+\gamma \) + jets production with Sherpa

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 \(Z\gamma \) production but also for the \(Z\gamma \) + 1-jet process we find significantly reduced systematic uncertainties and very good agreement with experimental measurements at \(\sqrt{s}=8\,\mathrm {TeV}\). Predictions at \(\sqrt{s}=13\,\mathrm {TeV}\) 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.