New supersymmetric contributions to t→cV

We calculate the electroweaklike one-loop supersymmetric contributions to the rare and flavor-violating decay of the top quark into a charm quark and a gauge boson: t→cV, with V=γ,Z,g. We consider loops of both charginos and downlike squarks (where we identify and correct an error in the literature) and neutralinos and uplike squarks (which have not been calculated before). We also account for left-right and generational squark mixing. Our numerical results indicate that supersymmetric contributions to t→cV can be up to 5 orders of magnitude larger than their standard model counterparts. However, they still fall short of the sensitivity expected at the next-generation top-quark factories. copyright 1997 The American Physical Society