T-]CWW AND WW-](T)OVER-BAR-C-BAR IN EXTENDED MODELS(T(C)OVER)

Jenkins has pointed out that the process t --> cW(+)W(-) is GIM suppre ssed in the standard model, In this note, we calculate the branching r atio for a wide range of models, in which the decay occurs at tree lev el through exchange of a scalar, fermion or vector. In the case of sca lar exchange, a scalar mass between 2m(W) and 200 GeV leads to a reson ant enhancement, giving a branching ratio as high as a few tenths of a percent. We then note that all of these models will also allow W+W- - -> <(t)over bar c> + <(tc)over bar>, and we calculate the single-top/s inle-charm production rate at the LHC. The rates are such that the bac kground from single-top/single-bottom production will probably swamp t he signal. (C) 1997 Published by Elsevier Science B.V.