SINGLE-TOP-QUARK PRODUCTION BELOW T(T)OVER-BAR THRESHOLD IN E- COLLISIONS(E)

A calculation of the reaction e+e- --> tbW-BAR at parton level in the Born approximation is presented in the framework of the standard model . We place emphasis on the production behaviour of the process e+e- -- > tbW-BAR below the ttBAR threshold and the dependence of its cross se ction on the CMS energy and top-quark mass. A comparison between the s ingle-top-quark and top-quark-pair production channel in e+e- collisio ns is made. We find that this process is significant for the search fo r the top-quark when the collider energy is less than the ttBAR thresh old but sufficient to produce tbW-BAR.