Measurement of the $t\bar{t}$ production cross-section in the lepton+jets channel at $\sqrt{s}=13\;$TeV with the ATLAS experiment

TL;DR

This paper reports a precise measurement of the top-antitop quark pair production cross-section in proton-proton collisions at 13 TeV using the ATLAS detector, confirming consistency with advanced QCD predictions.

Contribution

First measurement of the $t\bar{t}$ cross-section in the lepton+jets channel at 13 TeV with detailed systematic analysis.

Findings

Measured inclusive cross-section: 830 pb with 4.6% uncertainty.

Results agree with next-to-next-to-leading order QCD calculations.

Provided fiducial cross-section within experimental acceptance.

Abstract

The $t\bar{t}$ production cross-section is measured in the lepton+jets channel using proton$-$proton collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV collected with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 139 fb$^{-1}$. Events with exactly one charged lepton and four or more jets in the final state, with at least one jet containing $b$-hadrons, are used to determine the $t\bar{t}$ production cross-section through a profile-likelihood fit. The inclusive cross-section is measured to be ${\sigma_{\text{inc}} = 830 \pm 0.4~ \text{(stat.)}\pm 36~\text{(syst.)}\pm 14~\text{(lumi.)}~\mathrm{pb}}$ with a relative uncertainty of 4.6 %. The result is consistent with theoretical calculations at next-to-next-to-leading order in perturbative QCD. The fiducial $t\bar{t}$ cross-section within the experimental acceptance is also measured.