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

TL;DR

This paper introduces a sophisticated Monte Carlo generator for top-quark pair and single-top production at the LHC, incorporating NLO QCD corrections, spin correlations, off-shell effects, and interference, enhancing precision in top physics analyses.

Contribution

It presents a new NLO+PS generator that fully includes $tar{t}$ and $Wt$ processes with interference, using an improved matching method within the POWHEG framework.

Findings

Accurately models top-quark pair and single-top production with interference.

Includes off-shell and spin correlation effects for realistic simulations.

Facilitates precision top-quark mass measurements and background estimations.

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 $p p \to \ell^+\nu_{\scriptscriptstyle\ell}\, l^-\bar{\nu}_{\scriptscriptstyle l} b \bar{b}$ at NLO QCD, where the leptons $\ell$ and $l$ belong to different families, and $b$ quarks are massive. Thus, the contributions from $t\bar{t}$ and $Wt$ single-top production as well as their quantum interference 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 $Wt$ channel, and for $t\bar{t}$ and $Wt$ 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 POWHEGBOX framework.