Flavor changing neutral currents in ttbar decays at D\O

We present a search for flavor changing neutral currents (FCNC) in decays of top quarks. The analysis is based on a search for $t\bar{t}\rightarrow\ell'\nu\ell\bar{\ell}$+jets ($\ell, \ell' = e,\mu$) final states using 4.1 {\rm fb}$^{-1}$ of integrated luminosity of $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ {\rm TeV}. We extract limits on the branching ratio $B(t\rightarrow Zq)$ ($q = u, c$ quarks), assuming anomalous $tuZ$ or $tcZ$ couplings. We do not observe any sign of such anomalous coupling and set a limit of $B < 3.2$ at 95% C.L.