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

A bstract We present full off-shell NLO corrections in QCD obtained with the M o C a NLO 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 P ythia 8. 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.