The top-quark decay vertex in standard model extensions

New physics interactions can affect the strength and structure of the tbW vertex. We investigate the magnitudes and phases of anomalous contributions to this vertex in a two-Higgs doublet and the minimal supersymmetric extension of the standard model, and in a top-color assisted technicolor (TC2) model. While the magnitudes of the anomalous couplings remain below 1 percent in the first two models, TC2 interactions can reduce the left-chiral coupling f(L) by several percent.