First measurement of the top quark pair production cross section in proton-proton collisions at $\sqrt{s}=5.02~\mathrm{TeV}$

The top quark pair production cross section is measured for the first time in proton-proton collisions at $\sqrt{s} = 5.02~\mathrm{TeV}$, using data corresponding to an integrated luminosity of 26 pb$^{-1}$. The measurement is performed by analyzing events with at least one electron and one muon of opposite charge, and at least two jets. The measured cross section is $\sigma_{t\bar t} = 82 \pm 20 \mathrm{(stat)} \pm 5 \mathrm{(syst)} \pm 10 \mathrm{(lumi)} \: \mathrm{pb}$, in agreement with the expectation from the standard model.