Measurement of the tt̅ production cross-section in the lepton+jets channel at √s = 13 TeV with the ATLAS experiment

The top anti-top quark production cross-section is measured in the lepton+jets channel using proton–proton collision data at a centre-of-mass energy of √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 tt̅ production cross-section through a profile-likelihood fit. The inclusive cross-section is measured to be σ_inc = 830 ± 0.4 (stat.) ± 36 (syst.) ± 14 (lumi.) 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 tt̅ cross-section within the experimental acceptance is also measured.