Flavor-changing single top quark production channels at e(+)e(-) collidersin the effective Lagrangian description - art. no. 094016

We perform a global analysis of the sensitivity of CERN LEP2 and e(+)e(-) c olliders with a c.m. energy in the range 500-2000 GeV to new flavor-changin g single top quark production In the effective Lagrangian approach. The pro cesses considered are sensitive to new flavor-changing effective vertices s uch as Ztc, htc, and four-Fermi tcee contact term as well as a right-handed Wtb coupling. We show that e(+)e(-) colliders are most sensitive to the ph ysics responsible for the contact tcee vertices. For example, it is found t hat the recent data from the 189 GeV LEP2 run can be used to rule out any n ew flavor physics that can generate these four-Fermi operators up to energy scales of Lambda greater than or similar to 0.7-1.4 TeV, depending on the type of the four-Fermi interaction. We also show that a corresponding limit of Lambda greater than or similar to 1.3-2.5 and Lambda greater than or si milar to 17-27 TeV can be reached at the future 200 GeV LEP2 run and a 1000 GeV e(+)e(-) collider, respectively. We note that these Limits are much st ronger than the typical limits which can be placed on flavor diagonal four- Fermi couplings. Similar results hold for mu(+)mu(-) colliders and for t (u ) over bar associated production. Finally we briefly comment on the necessi ty of measuring all flavor-changing effective vertices as they can be produ ced by different types of heavy physics. [S0556-2821(99)01221-7].