Measurement of the top quark-pair production cross section with ATLAS in pp collisions at $\sqrt{s}=7$ TeV

A measurement of the production cross-section for top quark pairs (tt ??) in pp collisions at ???s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two dif- ferent topologies: single lepton (electron e or muon ??) with large missing transverse energy and at least four jets, and dilepton (ee, ???? or e??) with large missing transverse en- ???1 ergy and at least two jets. In a data sample of 2.9 pb , 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding ex- pected backgrounds from non-tt ?? Standard Model processes are estimated using data-driven methods and determined to be 12.2 ± 3.9 events and 2.5 ± 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM tt ?? production. The inclusive top quark pair pro- duction cross-section is measured to be +42 ??tt ?? = 145 ± 31(stat.)???27(syst.) pb. The measurement agrees with perturbative QCD calcula- tions.