NEUTRAL CURRENT FLAVOR CHANGING DECAYS FOR THE Z-BOSON AND THE TOP QUARK IN 2-HIGGS DOUBLET MODELS

We compute the magnitude of flavor changing neutral current (FCNC) decays of the t quark and of the Z boson expected in a two-Higgs doublet model. The charged Higgs boson couplings are constrained to be consistent with errors with K(L)-K(S) mixing, B(d)0-B(d)0BAR mixing, and the observed ratio of b --> u/b --> c decays. We find that large corrections to the predictions of the standard model are possible, but that even the maximum possible levels for FCNC decays are so small as to make their detection very difficult.