Abstract
At the LHC the CP properties of the top-quark Yukawa interaction can be probed through Higgs production in gluon fusion or in association with top quarks. We consider the possibility for both CP-even and CP-odd couplings to the top quark to be present, and study CP-sensitive observables at next-to-leading order (NLO) in QCD, including parton-shower effects. We show that the inclusion of NLO corrections sizeably reduces the theoretical uncertainties, and confirm that di-jet correlations in H+2 jet production through gluon fusion and correlations of the top-quark decay products in tbar{t}H production can provide sensitive probes of the CP nature of the Higgs interactions.
Highlights
While the path towards more and more precise determinations of the strength of the Yukawa interaction with the top is clear, the investigation of the structure and the properties of such interaction is considerably more open
In this work we have presented for the first time results at next-to-leading order (NLO) in QCD, including parton-shower effects, for the hadroproduction of a spin-0 particle with CP-mixed coupling to the top quark, in gluon-fusion plus one and two jets and in association with a top-quark pair
We have presented illustrative distributions obtained by interfacing NLO parton-level events to the HERWIG6 parton shower
Summary
While the path towards more and more precise determinations of the strength of the Yukawa interaction with the top (and of the Higgs boson couplings in general) is clear, the investigation of the structure and the properties of such interaction is considerably more open. The aim of this work is to present how EFT predictions accurate to next-to-leading order (NLO) in QCD matched to a parton shower can be used to determine the CP properties of the Higgs boson coupling to the top quark, through Higgs production in association with jets or with a pair of top quarks. To this aim we employ the Higgs Characterisation (HC) framework originally proposed in [15], which follows the general strategy outlined in [16] and has been recently applied to the VBF and VH channels [17]. We start from the definition of the effective lagrangian, pass to the identification of suitable benchmark scenarios, and to event generation at NLO in QCD accuracy, including parton-shower effects
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