Off-shell Top Quarks with One Jet at the LHC: A comprehensive analysis at NLO QCD

TL;DR

This paper provides a detailed NLO QCD analysis of top quark pair production with one jet at the 13 TeV LHC, including off-shell effects, backgrounds, and scale uncertainties, aiding new physics searches and top-quark measurements.

Contribution

It offers the first comprehensive NLO QCD predictions for off-shell top quarks with one jet, including all relevant contributions and uncertainties.

Findings

Results show significant off-shell and interference effects.

Scale variation impacts on differential cross sections are quantified.

Dynamical scale choices improve perturbative stability.

Abstract

We present a comprehensive study of the production of top quark pairs in association with one hard jet in the di-lepton decay channel at the LHC. Our predictions, accurate at NLO in QCD, focus on the LHC Run II with a center-of-mass energy of 13 TeV. All resonant and non-resonant contributions at the perturbative order ${\cal O}(\alpha_s^4 \alpha^4)$ are taken into account, including irreducible backgrounds to $t\bar{t}j$ production, interferences and off-shell effects of the top quark and the $W$ gauge boson. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. Additionally, we explore a few possibilities for a dynamical scale choice with the goal of stabilizing the perturbative convergence of the differential cross sections far away from the $t\bar{t}$ threshold. Results presented here are particularly relevant for searches of new physics as well as for precise measurements of the top-quark fiducial cross sections and top-quark properties at the LHC.