The simplest of them all: $t\bar{t} W^\pm$ at NLO accuracy in QCD

TL;DR

This paper presents a state-of-the-art NLO QCD calculation for the $tar{t}W^\pm$ process at the LHC, aiming to improve theoretical predictions and address discrepancies with experimental data.

Contribution

It provides the first comprehensive NLO QCD computation including off-shell effects, interference, and various contributions for $tar{t}W^\pm$ production at 13 TeV.

Findings

NLO corrections significantly affect cross section predictions.

Off-shell effects alter the $tar{t}W^\pm$ cross section compared to the narrow-width approximation.

Results include detailed fiducial and differential cross sections for different scales and PDFs.

Abstract

Recent measurements of the $pp\to t\bar{t}W^\pm$ process in multi-lepton final states, as performed by the ATLAS collaboration in the context of the Higgs boson studies in the $t\bar{t}H$ channel, have shown discrepancies between theoretical predictions and experimental data. Such discrepancies have been observed both in the overall normalisation as well as in the modelling of the $t\bar{t}W^\pm$ process. With the goal of understanding and resolving the modelling issues within the SM $t\bar{t}W^\pm$ process we report on the state-of-the-art NLO QCD computation for this process. Specifically, we calculate higher-order corrections to the $e^+ \nu_e \,\mu^-\bar{\nu}_\mu \, e^+ \nu_e \, b\bar{b}$ and $e^- \bar{\nu}_e \, \mu^+ {\nu}_\mu \, e^- \bar{\nu}_e \, b\bar{b}$ final state at the LHC with $\sqrt{s}=13$ TeV. In the computation off-shell top quarks are described by Breit-Wigner propagators, furthermore, double-, single- as well as non-resonant top-quark contributions along with all interference effects are consistently incorporated at the matrix element level. Results at NLO QCD accuracy are presented in the form of fiducial integrated and differential cross sections for two selected renormalisation and factorisation scale choices and three different PDF sets. The impact of the top quark off-shell effects on the $t\bar{t}W^\pm$ cross section is also examined by an explicit comparison to the narrow-width approximation.