Production of four heavy quarks and $B_c$-mesons at the $Z^0$-boson pole

Abstract

The cross-section for the production of $b\bar{b}c\bar{c}$ quarks in $e^{+}{e}^{-}$ annihilation, that proves to be at a level of $\sigma (e^{+}{e}^{-}\to b\bar{b}c\bar{c})/\sigma (e^{+}{e}^{-}\to b\bar{b})\sim 10^{-2}$ for $\sqrt{s}=M_Z$ is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of $1S$- and $2S$-wave states of $B_c$-meson in the reaction $e^{+}{e}^{-}\to B_{c}b\bar{c}$ were calculated in the nonrelativistic model of a heavy quarkonium. The fragmentation function of $b\to B_c^{(\ast )}$ is analysed in the scaling limit. The number of ${\Lambda }_{bc}$-hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality.

Standard LATEX 16 pages, 10 Figs. (unavalibale)