We present a new method to measure the top quark pair production cross section and the background rates with 2.7 fb$^{-1}$ of data from $pbar{p}$ collisions at $sqrt{s} =1.96$ TeV collected with the CDF II Detector. The size of the dataset was chosen to directly show the improvements of this new method. We select events with a single electron or muon, missing transverse energy, and at least one b-tagged jet. We perform a simultaneous fit to a jet flavor discriminant across nine samples defined by the number of jets and b-tags. We measure a top cross section of $sigma_{tbar{t}} = 7.64 pm 0.57 mathrm{(stat + syst)} pm 0.45 mathrm{(luminosity)}$ pb. An advantage of this approach is that many systematic uncertainties are measured in situ and inversely scale with integrated luminosity.
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