The dileptonic decay channel of the top-quark pair production at LHC is the best candidate for an early observation of a process involving top-quark. Due to its clean signature (two isolated and high-pT leptons with opposite charge, two b-jets and missing transverse energy) and its large cross-section, the expected background events can be sufficiently reduced to allow a rediscovery after few inverse picobarns of integrated luminosity. This presentation describes the result of a Monte Carlo study done at √s = 10TeV under the assumption 10 pb−1 of integrated luminosity in the CMS experiment. It presents the expected precision on the cross-section measurement and covers the description of the simulation and the
backgrounds, the event selection, the data-driven background estimation methods, the systematic uncertainties and two alternative analyses (tracker-based and b-quark
content)
