Testing flavor-changing neutral currents in the rare top quark decayst→cViVj

Abstract

We discuss the Flavor-Changing Neutral Current (FCNC) decays of the top quark t -> c Vi Vj (Vi=gamma, Z, g) in the framework of the Standard Model (SM) and in a two-higgs doublet model (2HDM) with tree-level FCNC couplings. While in the SM the expected branching ratios are extremelly small, in the 2HDM they may be sizable, of order 10^(-5) - 10^(-5), and thus accesible at the CERN LHC. We conclude with the interesting observation that the FCNC decay modes may not be equally suppressed as their corresponding decays t ->c Vi in this 2HDM.