Top quark flavor-changing neutral currents at CERN LEP-200: Signals and backgrounds

Abstract

Current experimental limits on FCNC allow for the single top quark production process at CERN LEP-200. We show that the rates from standard model electroweak diagrams are negligible. In order to estimate the background due to misidentification of the b quark, we calculate the 4-quark process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}c\overline{s}\ifmmode \bar{u}\else \={u}\fi{}d$ within the EW sector of the SM. We show that it is possible to handle this background using different kinematical cuts on the quarks. We conclude that LEP-200 offers the possibility of improving the current bounds on flavor-violating couplings but that one will likely have to work with semileptonic decay modes of the top quark in order to avoid rather large QCD backgrounds.