Search for Single Top Quarks Produced via Flavor-Changing Neutral-Current Couplings at D\O

The large mass of the top quark, close to the electroweak symmetry-breaking scale, makes it a good candidate for probing physics beyond the Standard Model, including possible anomalous couplings. One form these couplings can take is with flavor-changing neutral currents, which can give rise to a single top quark in the final state through gluon exchange, together with a $c$ or $u$ quark in the initial or final state. We search for single top quark production through both the $t$-$c$-$g$ and $t$-$u$-$g$ couplings, using the D\O\ detector at the Fermilab Tevatron collider, and present limits on the anomalous coupling parameters $\kappa_c/\Lambda$ and $\kappa_u/\Lambda$, where $\Lambda$ defines the scale of new physics and $\kappa_c$ ($\kappa_u$) defines the strength of the $t$-$c$-$g$ ($t$-$u$-$g$) couplings.