SINGLE TOP PRODUCTION AT THE NEXT-GENERATION LINEAR E(+)E(-) COLLIDERS

Present limits on the top mass from LEP1 and Tevatron point to a top quark that is considerably heavier than the W vector boson in the standard model; e+ e- colliders with square-root s congruent-to 300 GeV (the c.m. energy foreseen at the first phase of the next linear e+ e- collider) could be well below the energy threshold for real top-pair production. We argue that, if this is the case, single top production through the process e+ e--->tbW-BAR(tbW+BAR), where tbBAR(tbBAR) are produced mainly by means of a virtual W, becomes the dominant top production mechanism. Total cross sections and kinematical distributions are evaluated and numerical results are given in ranges of m(t) and square-root s where single top production can be of relevance. The relative importance of virtual-W and virtual-t contributions to the process is discussed.