Resonance-aware parton-shower matching for off-shell top-antitop production with semi-leptonic decays at electron-positron colliders

Abstract: We present full off-shell NLO corrections in QCD obtained with the MoCaNLO code matched to parton shower. A resonance-aware matching procedure has been devised for the MC@NLO method tuned to the Catani-Seymour dipole subtraction. Specifically, we consider the off-shell production of a top-antitop pair in the semi-leptonic decay channel in electron-positron collisions and match it to the final-state QCD parton shower of PYTHIA8. Distortions of resonances' line shapes are avoided by providing the details of the resonance-cascade chain on an event-by-event basis to the parton shower and by adapting the matching accordingly through the introduction of dedicated counterterms.