Measurement of the tt̄ production cross section in pp collisions at √s=7TeV in dilepton final states containing a τ

The top quark pair production cross section is measured in dilepton events with one electron or muon, and one hadronically decaying τ lepton from the decay tt¯→(lνl)(τhντ)bb¯, (l=e, μ). The data sample corresponds to an integrated luminosity of 2.0 fb−1 for the electron channel and 2.2 fb−1 for the muon channel, collected by the CMS detector at the LHC. This is the first measurement of the tt¯ cross section explicitly including τ leptons in proton-proton collisions at s√=7 TeV. The measured value σtt¯=143±14(stat)±22(syst)±3(lumi) pb is consistent with the standard model prediction