An NLO+PS generator for $${\varvec{t \bar{t}}}$$ t t ¯ and $${\varvec{W t}}$$ W t production and decay including non-resonant and interference effects

Abstract

We present a Monte Carlo generator that implements significant theoretical improvements in the simulation of top-quark pair production and decay at the LHC. Spin correlations and off-shell effects in top-decay chains are described in terms of exact matrix elements for pp → + ν l −ν l bb at order α 4 α 2 S plus full NLO QCD corrections, where the leptons and l belong to different families, and b quarks are massive. Thus, the contributions from tt and W t single-top production, plus contributions without top resonances and all relevant quantum interferences between different channels are fully included. Matrix elements are matched to the Pythia8 parton shower using a recently proposed method that allows for a consistent treatment of resonances in the POWHEG framework. These theoretical improvements are especially important for the interpretation of precision measurements of the top-quark mass, for single-top analyses in the W t channel, and for tt and W t backgrounds in the presence of jet vetoes or cuts that enhance off-shell effects. The new generator is based on a process-independent interface of the OpenLoops amplitude generator with the POWHEG-BOX framework.

Top-bottom interference effects in Higgs boson production

“…Refs. [12,13]) and as an input for the real-virtual contributions in NNLO computations (see e.g. Ref.…”

Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

“…[78] and [79,80] resonance aware matching has been proposed within the MC@NLO and Powheg frameworks respectively, with focus on narrow coloured resonances. In our configuration the resonances are broader and the interference plays a more important role.…”

NLO QCD predictions for off-shell t t ¯ $$ t\overline{t} $$ and t t ¯ H $$ t\overline{t}H $$ production and decay at a linear collider

“…[35], the process pp → bb4f has been matched consistently to parton showers, as presented recently in ref. [36]. For hadron colliders, corresponding NLO QCD corrections to top-quark pair production in association with a Higgs boson [37] or a jet [38,39] including leptonic decays have also been studied.…”

“…Finally we want to note, that the resonance-aware FKS subtraction scheme, including a definite resonance history assignment in the event output, enables a consistent matching of fixed-order NLO predictions with parton shower generators for processes with intermediate resonances [35,36]. To this end, all relevant resonance histories should be taken into account.…”