Flavor-changing Top Quark Decays In MSSM Without R-Parity

The flavor changing top quark decays $t \to cV $ ($V=Z,\gamma, g$) induced by R-parity-violating couplings in the minimal supersymmetric standard model (MSSM) are evaluated. We find that the decays $t \to cV$ can be significantly enhanced relative to those in the R-parity conserving SUSY model. Our results show that the top quark FCNC decay can be as large as $Br(t \to cg) \sim 10^{-3}$, $Br(t \to cZ) \sim 10^{-4}$ and $Br(t \to c\gamma)\sim 10^{-5}$, which are observable at the upgraded Tevatron and the LHC.