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. Hence, ee colliders with √ s ≃ 300 GeV (the c.m. energy foreseen at the first phase of the Next Linear ee 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−→ tb̄W−(t̄bW ), where tb̄(t̄b) 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 mt and √ s where single top production can be of relevance. The relative importance of virtual-W and virtual-t contributions to the process is discussed. 1 e-mail address: [email protected] 2 e-mail address: [email protected] S. Ambrosanio, B. Mele / Single top production 1