Search for the Flavor Changing Neutral Current Decay t $\to Zq$ in $p   \bar{p}$ Collisions at $\sqrt{s}=1.96$
  We report a search for the flavor changing neutral current (FCNC) decay of the top quark \tZq ($q=u,c$) in \ppbar collisions at $\sqrt{s} = 1.96\tev$ using a data sample corresponding to an integrated luminosity of 1.9\invfb collected by the CDF II detector. This decay is strongly suppressed in the standard model (SM) and an observation of a signal at the Tevatron would be an indication of physics beyond the SM. Using $Z+\ge4$ jet final state candidate events, both with and without an identified bottom quark jet, we discriminate signal from background by exploiting kinematic constraints present in FCNC events and obtain an upper limit of $\btZq < 3.7%$ at 95% C.L. 
CDF Collaboration: T.Aaltonen, et al