Modelling of loop-induced $ZH$-production in ATLAS

This talk presents and compares Monte Carlo generator predictions for the loop-induced production of a Higgs boson $H$ in association with a Z boson that are used in ATLAS. Two separate matrix element calculations of the loop-induced $ZH$ process with up to one additional jet are performed at leading order in the strong coupling constant and matched to parton showers, using Sherpa and MadGraph_aMC@NLO+Pythia 8. These predictions are contrasted with a Powheg-Box+Pythia 8 simulation of the inclusive loop-induced $ZH$ process at leading order. The comparison highlights important kinematic differences, particularly in the regime of boosted Higgs-boson decays. This suggests that the new simulations including one extra emission at the matrix-element level documented here offer a more accurate characterisation of this process.