t-tbar Pair production cross section measurement at the LHC

Measurement of $t\bar{t}$ pair production cross sections with an integrated luminosity of around 1 fb$^{-1}$ at $\sqrt{s}$ = 7 TeV obtained with the ATLAS and CMS detectors are reported. The inclusive cross sections in dilepton (ee, $e\mu$, $\mu\mu$ and $\mu\tau$), lepton+jets (e, $\mu$) and all hadronic decay modes are measured. In addition to inclusive cross section measurement, the study of jet multiplicity with additional jets are also presented, which is important to constrain the initial state radiation. Measurement of the charge asymmetry at the LHC is also presented. All measurements are compatible with Standard Model predictions.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 5 pages, 7 figure