Measurement of the $t\bar{t}$ production cross-section using dilepton events in $pp$ collisions at $\sqrt{s}=5.02$ TeV with the ATLAS detector

The inclusive top quark pair ($t\bar{t}$) production cross-section $\sigma_{t \bar{t}}$ has been measured in proton-proton collisions at $\sqrt{s}=5.02$ TeV, using 257 pb$^{-1}$ of data collected in 2017 by the ATLAS experiment at the LHC. Using events with an opposite-charge pair of leptons and $b$-tagged jets, the cross-section is measured to be $\sigma_{t\bar{t}}=66.0\pm 4.5\pm 1.6\pm 1.2\pm 0.2$ pb, where the four uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the LHC beam energy, giving a total uncertainty of 7.5%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order, and is compared to predictions using different proton parton distribution functions.