The production of a [formula omitted] or [formula omitted] quark pair by e+e- collision based on the standard model and its extensions

Abstract

Keeping all the terms of heavy flavor masses up to the leading order, and bearing in mind that (i) the massive top m t ⩾ 100 GeV, (ii) the possible energies: S=200 GeV at LEP-II and a higher one S=500 GeV , we carry out precise calculations on the single top-quark production e ++e - → t + c( t+c) in the framework of the minimal Standard Model (MSM) and its extensions (of four generations and one or two Higgs doublets), to see the possible sense of the single-top production for the colliders. The results show that the process is unmeasurably small for both the MSM and the extension with four generations of fermions but only one Higgs doublet; however, it is possibly measurable for the extensions with two Higgs doublets and particularly favorable parameter values even at LEP-II.