NLO QCD corrections to off-shell $\text{t}\bar{\text{t}}\text{W}^+$ production at the LHC

TL;DR

This paper computes NLO QCD corrections for off-shell top-antitop and W+ production at the LHC, including all effects, and compares full and approximate methods to assess accuracy in different phase space regions.

Contribution

It provides the first full off-shell NLO QCD calculation for t-tbar W+ production, including all off-shell, spin, and interference effects, and compares it with a double-pole approximation.

Findings

NLO QCD corrections increase cross-section by about 20%.

Distributions show large K-factors in suppressed phase space regions.

Double-pole approximation agrees within a few percent for total cross-section but can differ significantly in certain regions.

Abstract

We present results of a computation of NLO QCD corrections to the production of an off-shell top--antitop pair in association with an off-shell $\text{W}^+$ boson in proton--proton collisions. As the calculation is based on the full matrix elements for the process $\text{p}\text{p}\to {\text{e}}^+\nu_{\text{e}}\,\mu^-\bar{\nu}_\mu\,\tau^+\nu_\tau\,{\text{b}}\,\bar{\text{b}}$, all off-shell, spin-correlation, and interference effects are included. The NLO QCD corrections are about $20\%$ for the integrated cross-section. Using a dynamical scale, the corrections to most distributions are at the same level, while some distributions show much larger $K$-factors in suppressed regions of phase space. We have performed a second calculation based on a double-pole approximation. While the corresponding results agree with the full calculation within few per cent for integrated cross-sections, the discrepancy can reach $10\%$ and more in regions of phase space that are not dominated by top--antitop production. As a consequence, on-shell calculations should only be trusted to this level of accuracy.