Expectations for observation of top quark pair production in the dilepton final state with the early CMS data at sqrt s = 10 TeV

Expectations for the observation of top-quark pair production in proton-proton collisions at the \lhcE{10} with two leptons (electron or muon) in the final state are presented. The emphasis is put on an analysis strategy for the early phase of CMS operation with data corresponding to an integrated luminosity of $10 \pbinv$. The Standard Model signal and background sources are surveyed for a selection based on the requirement of two leptons (electron or muon) in the final state, at least two hadronic jets and missing transverse energy. A clear signal stands out, and the signal cross section can be measured with a statistical uncertainty of about $15\%$ and a systematic uncertainty close to $10\%$ excluding the uncertainty on the integrated luminosity, which is expected to be $10\%$. A complementary approach is also presented for the early phase of operation which relies on jets reconstructed in the tracker and does not make use of the missing transverse energy observable. A good signal sensitivity can be obtained with such a selection which relies minimally on the calorimeter measurements. Having established simple and robust analysis strategies for the early phase, the possibility to further gain in sensitivity by exploiting the $b$-quark content of the events is studied for an integrated luminosity of $100\pbinv$.