A search for t→τνq in tt¯ production

We present a search for tt¯ events with a tau lepton in the final state. The data sample corresponds to an integrated luminosity of 194 pb−1 collected with the CDF II detector from pp¯ collisions at a center of mass energy of 1.96 TeV. We observe two events with an expected signal of 1.0±0.2 events and a background of 1.3±0.3 events. We determine a 95% confidence level upper limit on rτ, the ratio of the measured rate of t→τνq to the expectation, of 5.2.