Combination of ATLAS and CMS top-quark pair cross section measurements using proton-proton collisions at sqrt(s) = 7 TeV

% A combination of top-quark pair production cross-section ($\sigma_{\rm t\bar t}$) measurements at a centre-of-mass energy of 7~TeV performed by the ATLAS and CMS experiments at the LHC is presented. The combination includes $\sigma_{\rm t\bar t}$ measurements in the lepton+jets, di-lepton, and all jets channels which use between 0.7 and 1.1~fb$^{-1}$ of proton-proton collisions. The combined preliminary LHC measurement of the top-quark pair production cross-section is $\sigma_{\rm t\bar t} = 173.3 \pm 2.3~\mathrm{(stat.)} \pm 7.6~\mathrm{(syst.)} \pm 6.3~\mathrm{(lumi.)}~\mathrm{pb} = 173.3 \pm 10.1~\mathrm{pb}$ for a top-quark mass of $172.5\mathrm{\ GeV}/c^2$, corresponding to a total uncertainty of 5.8\%. The result is in agreement with the standard model prediction.