Top - Charm Associated Production in High Energy

The possibility of exploring the flavor changing neutral current tcZ/tcγ couplings in the production vertex for the reaction e+e− → tc̄ + t̄c is examined. Using a model independent parameterization for the effective Lagrangian to describe the most general three-point interactions, production cross sections are found to be relatively small at LEP II, but potentially sizeable 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 couplings at LEP II with an integrated luminosity of 4 × 500 pb−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 fb−1 luminosity, one expects to reach a sensitivity at or below the percentage level. ∗Work supported by the Department of Energy, Contract DE-AC03-76SF00515