Measurement of thett¯production cross section inpp¯collisions ats=1.96 TeVusing kinematic fitting ofb-tagged lepton+jet events

We report a measurement of the $t\overline{t}$ production cross section using the CDF II detector at the Fermilab Tevatron. The data consist of events with an energetic electron or muon, missing transverse energy, and three or more hadronic jets, at least one of which is identified as a $b$-quark jet by reconstructing a secondary vertex. The background fraction is determined from a fit of the transverse energy of the leading jet. Using $162\pm 10{\mathrm{pb}}^{-1}$ of data, the total cross section is found to be $6.0\pm 1.6(\mathrm{stat}.)\pm 1.2(\mathrm{syst}.)\mathrm{pb}$, which is consistent with the standard model prediction.