Double Flavor Violating Top Quark Decays in Effective Theories

The possibility of detecting double flavor violating top quark transitions $t \to u_i\tau \mu$ ($u_i=u,c$) is explored in a model--independent manner, using the effective Lagrangian approach. Low--energy data, on high precision measurements, and current experimental limits are used to constraint the $tu_iH$ and $H\tau \mu$ vertices and then to calculate the branching ratio BR$(t \to u_i\tau \mu)$. If in the Standard Model BR$(t \to u_i\tau \mu)$ is of the order of $10^{-13}$$-10^{-14}$, higgs--mediated double flavor violating top quark decays can occur with branching ratios ranging from $10^{-3}$ to $10^{-4}$ for 114.4 GeV$/c^2$ $< m_H<$ $2m_W$, that is at the reach of the CERN Large Hadron Collider.