Towards the measurement of the ttbar cross section in the e-tau and mu-tau dilepton channels in pp collisions at sqrt(s)=14 TeV

The potential for measuring the $t\bar{t}$ production cross section with the first $100 \rm\ pb^{-1}$ of integrated luminosity accumulated by the CMS detector is studied in \ttbar dilepton events with one electron or muon and one hadronically decaying tau lepton. The goal is the measurement of the cross section ratio, $\sigma[t\bar t \rightarrow (l\nu)(\tau\nu_{\tau})b\bar b]$/$\sigma[t\bar t \rightarrow (l\nu)(l\nu)b\bar b]$ with $(l=e,\mu)$, where many systematic uncertainties cancel out. Detector conditions are simulated with the expected performance of the CMS detector for the early data taking phase. Event selection and strategies to estimate backgrounds from data are investigated.