Combination of ATLAS and CMS top-quark pair cross-section measurements in the e$\mu$ final state using proton-proton collisions at $\sqrt{s} = 8$ TeV

A combination of top-quark pair production cross-section (σ tt ¯ ) measurements at a centre-of-mass energy of 8 TeV performed by the ATLAS and CMS experiments at the LHC in the di-lepton channels is presented. The σ tt ¯ measurements use between 5.3 and 20.3 fb −1 of proton-proton collisions. The combined preliminary LHC measurement of the top-quark pair production cross-section is σ tt ¯ =241.4±1.4 (stat.)±5.7 (syst.)±6.2 (lumi.) pb=241.4±8.5 pb for a top-quark mass of 172.5 GeV , corresponding to a total uncertainty of 3.5%. The result is in agreement with the standard model prediction