A measurement of the production cross-section for top quark pairs (t (t) over bar) in pp collisions at root s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron e or muon mu) with large missing transverse energy and at least four jets, and dilepton (ee, mu mu or e mu) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb(-1), 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-t (t) over bar 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 t (t) over bar production. The inclusive top quark pair production cross-section is measured to be sigma(t (t) over bar) = 145 +/- 31 (stat.)(-27)(+42) (syst.) pb. The measurement agrees with perturbative QCD calculations. RI Doyle, Anthony/C-5889-2009; Fazio, Salvatore /G-5156-2010; Bauer, Florian/G-8816-2011; valente, paolo/A-6640-2010; Jones, Roger/H-5578-2011; Gutierrez, Phillip/C-1161-2011; Marti-Garcia, Salvador/F-3085-2011; Ferrando, James/A-9192-2012; collins-tooth, christopher/A-9201-2012; Perrino, Roberto/B-4633-2010; De Cecco, Sandro/B-1016-2012; Stoicea, Gabriel/B-6717-2011; branchini, paolo/A-4857-2011; Wolter, Marcin/A-7412-2012; Rotaru, Marina/A-3097-2011; O'Shea, Val/G-1279-2010; Nemecek, Stanislav/C-3487-2012; Robson, Aidan/G-1087-2011; Takai, Helio/C-3301-2012; St.Denis, Richard/C-8997-2012; Britton, David/F-2602-2010; Pina, Joao /C-4391-2012; Li, Xuefei/C-3861-2012; Smirnova, Lidia/D-8089-2012; Smirnov, Sergei/F-1014-2011; Gladilin, Leonid/B-5226-2011; Kramarenko, Victor/E-1781-2012; Prokoshin, Fedor/E-2795-2012; Alexa, Calin/F-6345-2010; Pacheco Pages, Andres/C-5353-2011; Moorhead, Gareth/B-6634-2009; Livan, Michele/D-7531-2012; Petrucci, Fabrizio/G-8348-2012; Wemans, Andre/A-6738-2012; Fabbri, Laura/H-3442-2012; Kurashige, Hisaya/H-4916-2012; Losada, Marta/B-2261-2010; Castro, Nuno/D-5260-2011; Jakubek, Jan/E-6530-2011; Andreazza, Attilio/E-5642-2011; Kladiva, Eduard/G-6305-2011; Villa, Mauro/C-9883-2009; Kuzhir, Polina/H-8653-2012; Delmastro, Marco/I-5599-2012

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at root s=7 TeV