Search for Top-Quark Production via Flavor-Changing Neutral Currents inW+1Jet Events at CDF

We report on a search for the non-standard-model process $u(c)+g\to t$ using $p\overline{p}$ collision data collected by the Collider Detector at Fermilab II detector corresponding to $2.2{\mathrm{fb}}^{-1}$. The candidate events are classified as signal-like or backgroundlike by an artificial neural network. The observed discriminant distribution yields no evidence for flavor-changing neutral current top-quark production, resulting in an upper limit on the production cross section $\sigma \mathbf{(}u(c)+g\to t\mathbf{)}<1.8\mathrm{pb}$ at the 95% C.L. Using theoretical predictions we convert the cross section limit to upper limits on flavor-changing neutral current branching ratios: $\mathcal{B}(t\to u+g)<3.9\times {10}^{-4}$ and $\mathcal{B}(t\to c+g)<5.7\times {10}^{-3}$.