Combination of ATLAS and CMS top-quark pair cross section measurements using up to 1.1 fb-1 of data at 7 TeV

A combination of top-quark pair production cross-section 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 ttbar measurements in the lepton+jets, di-lepton, and all-jets channels which use between 0.7 and 1.1/fb of proton-proton collisions. The combined preliminary LHC measurement of the top-quark pair production cross-section is sigma(ttbar) = 173.3 ± 2.3 (stat.) ± 7.6 (syst.) ± 6.3 (lumi.) pb = 173.3 ± 10.1 pb for a top-quark mass of 172.5 GeV, corresponding to a total uncertainty of 5.8%. The result is in agreement with the standard model prediction.