Top-Quark Pair Production and Decay in Extended Higgs Sectors

Abstract

Extensions of the Higgs sector in the Standard Model address outstanding questions like the first-order electroweak phase transition and also present a rich collider phenomenology. The two-Higgs-doublet model is a minimal extension of the Standard Model with an extra complex $SU(2)_L$ doublet, and consists of an extra scalar, a pseudoscalar and a pair of charged Higgs bosons along with a Standard-Model-like Higgs boson. We present a modified version of the hvq library of the POWHEG-BOX-V2 event generator interfaced with the OpenLoops 2 amplitude generator to obtain predictions for top-quark pair production at NLO accuracy, including top-quark decays with full spin correlations in a framework that extends the SM Higgs sector with an extra heavy scalar and a pseudoscalar. The interference effects between the scalar and pseudoscalar signals, and the Standard Model QCD background are implemented. We include parton showers and hadronisation, and take detector effects into consideration. The status of our work and plans to extend it to future collider projects are discussed.