Measurement of the cross section of top quark-antiquark pair production in association with a W boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports the most precise measurement to date of the production cross section of top quark-antiquark pairs in association with a W boson at 13 TeV, using CMS data and advanced analysis techniques.

Contribution

It provides the first comprehensive measurement of $ ext{t}ar{ ext{t}}$W production cross sections, including separate results for $ ext{t}ar{ ext{t}}$W$^+$ and $ ext{t}ar{ ext{t}}$W$^-$, with improved accuracy.

Findings

Measured inclusive $ ext{t}ar{ ext{t}}$W cross section: 868 ± 40 (stat) ± 51 (syst) fb.

Measured $ ext{t}ar{ ext{t}}$W$^+$ and $ ext{t}ar{ ext{t}}$W$^-$ cross sections: 553 ± 30 (stat) ± 30 (syst) fb and 343 ± 26 (stat) ± 25 (syst) fb.

The ratio of $ ext{t}ar{ ext{t}}$W$^+$ to $ ext{t}ar{ ext{t}}$W$^-$ is 1.61 ± 0.15 (stat) ± 0.07 (syst).

Abstract

The production of a top quark-antiquark pair in association with a W boson ($\mathrm{t\bar{t}}$W) is measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The analyzed data was recorded by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 fb$^{-1}$. Events with two or three leptons (electrons and muons) and additional jets are selected. In events with two leptons, a multiclass neural network is used to distinguish between the signal and background processes. Events with three leptons are categorized based on the number of jets and of jets originating from b quark hadronization, and the lepton charges. The inclusive $\mathrm{t\bar{t}}$W production cross section in the full phase space is measured to be 868 $\pm$ 40 (stat) $\pm$ 51 (syst) fb. The $\mathrm{t\bar{t}}$W$^+$ and $\mathrm{t\bar{t}}$W$^-$ cross sections are also measured as 553 $\pm$ 30 (stat) $\pm$ 30 (syst) and 343 $\pm$ 26 (stat) $\pm$ 25 (syst) fb, respectively, and the corresponding ratio of the two cross sections is found to be 1.61 $\pm$ 0.15 (stat) $^{+0.07}_{-0.05}$ (syst). The measured cross sections are larger than but consistent with the standard model predictions within two standard deviations, and represent the most precise measurement of these cross sections to date.