Abstract
The tt− production cross section (σtt−) is measured in proton-proton collisions at s√=7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 fb−1. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of σtt− for a top-quark mass of 172.5 GeV is 161.9±2.5(stat.)+5.1−5.0(syst.)±3.6(lumi.)pb , consistent with the prediction of the standard model.