Higgs and Z boson associated production via gluon fusion in the SM and the 2HDM

Abstract: We analyse the associated production of Higgs and Z boson via heavy-quark loops at the LHC in the Standard Model and beyond. We first review the main features of the Born 2 → 2 production, and in particular discuss the high-energy behaviour, angular distributions and Z boson polarisation. We then consider the effects of extra QCD radiation as described by the 2 → 3 loop matrix elements, and find that they dominate at high Higgs transverse momentum. We show how merged samples of 0- and 1-jet multiplicities, matched to a parton shower can provide a reliable description of differential distributions in ZH production. In addition to the Standard Model study, results in a generic two-Higgs-doublet-model are obtained and presented for a set of representative and experimentally viable benchmarks for Zh0, ZH0 and ZA0 production. We observe that various interesting features appear either due to the resonant enhancement of the cross-section or to interference patterns between resonant and non-resonant contributions.