Top quark pair production in association with a jet with NLO parton showering

TL;DR

This work demonstrates the first application of a POWHEG_BOX–HELAC framework to produce NLO accuracy cross sections for ttbar+jet matched to parton showers, enabling hadron-level predictions with showered decays. It validates the approach against established NLO results, explores the impact of decays and showering on key observables, and provides LHC predictions under realistic selection criteria. The study highlights the necessity of full parton shower, hadronization, and decay modeling to accurately describe distributions, while also noting limitations such as the neglect of spin correlations in decays within the current PS treatment. The generated unweighted events offer a practical resource for analyses at the Tevatron and LHC and establish a generalizable framework for NLO+PS predictions of complex final states.

Abstract

We compute the production cross section of a top-antitop pair in association with a jet at hadron colliders at next-to-leading order accuracy matched with parton shower algorithms to make predictions at the hadron level. The parton shower allows for including the decay of the top quarks at the leading order accuracy. We use a framework based on three well established numerical codes, the POWHEG-BOX, used for the calculation of the cross section, HELAC, which generates the matrix elements for the Born-level, real emission and the virtual part, and finally a parton shower program, such as PYTHIA or HERWIG, which generate the parton-shower and hadronization.

Figures (7)

• Figure 1: Transverse momentum and rapidity distributions of the jet.
• Figure 2: Transverse momentum and rapidity distributions of the antilepton.
• Figure 3: Distribution of the scalar sum of transverse momenta.
• Figure 4: Transverse momentum distributions of the first, second and third hardest jet.
• Figure 5: Rapdity distribution of the antilepton. The lower plot also includes the ratio of the cross section obtained with $\mu = m_{\rm t}$ to that obtained with $\mu = m_{\perp}$ (PowHel+PYTHIA).