  We present theoretical predictions for mono-$Z$ production in the search for
dark matter in Run-II at the LHC, including next-to-leading order QCD
corrections and parton-shower effects. We consider generic simplified models
with vector and scalar $s$-channel mediators. The calculation is performed by
implementing the simplified models in the FeynRules/MadGraph5_aMC@NLO
framework, which allows us to include higher-order QCD corrections and
parton-shower effects in an automated way. We find that these corrections are
sizeable and help to reduce the theoretical uncertainties. We also investigate
the discovery potential in several benchmark scenarios in the 13 TeV run at the
LHC.
