e+e-→b(b)over-bar-u(d)over-barμ-(ν)over-barμ with a t(t)over-bar production

The cross section of e(+)e(-) --> b (b)over-bar-u (d)over-bar mu(-)(mu)over-bar(mu) process with a complete set of tree diagrams, 232 diagrams in the unitary gauge, was calculated at the energy range of root 3 -340-500 GeV by using GRACE system. ii main contribution IO the cross section comes from (tt)over-bar production, where t and (t)over-bar decay into mu (d)over-bar and (b)over-bar mu(-)(mu)over-bar(mu), respectively. It was found that the interference between the diagrams with (tt)over-bar production and those with single-t through WW pair production amounts to 10% at the (tt)over-bar threshold energy region. In the energy region above twice of the top quark mass, more than 95% of the cross section comes from the (tt)over-bar diagrams. (C) 1997 Elsevier Science B.V.