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

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~$\text{(lumi.)}$~$\mathrm{p}\mathrm{b}$}$ 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.