Flavour Changing Neutral Currents, Weak-Scale Scalars and Rare Top Decays

Abstract

We examine the decays $t\rightarrow cγ$ and $c Z^0$ in the Standard Model with an extra scalar doublet and no discrete symmetry preventing tree-level flavour changing neutral currents. The Yukawa couplings of the new scalars are assumed to be proportional to fermion masses, evading bounds on FCNC's from the light quark sector. These rare top decays may be visible at the SSC.