Top-charm associated production in high energye+e−collisions

The possibility of exploring the flavor changing neutral current $tcZ/tc\gamma$ couplings in the production vertex for the reaction $e^{+}{e}^{-}\to t\overline{c}+\overline{t}c$ is examined. Using a model independent parametrization for the effective Lagrangian to describe the most general three-point interactions, production cross sections are found to be relatively small at CERN LEP II, but potentially sizable at higher energy $e^{+}{e}^{-}$ colliders. The kinematic characteristics of the signal are studied and a set of cuts are devised for clean separation of the signal from background. The resulting sensitivity to anomalous flavor changing coupling at LEP II with an integrated luminosity of $4\times 500{\mathrm{pb}}^{\mathrm{-}1}$ is found to be comparable to their present indirect constraints from loop processes, while at higher energy colliders with 0.5–1 TeV center-of-mass energy and 50–200 ${\mathrm{fb}}^{\mathrm{-}1}$ luminosity, one expects to reach a sensitivity at or below the percentage level.