Fragmentation of Heavy Quarks Produced ine+e−Annihilation

Identification of muons in hadronic events from $e^{+}{e}^{-}$ annihilation observed in the MAC detector at the storage ring PEP provides flavor tagging of heavy primary quarks. A sample enriched in events from $b\overline{b}$ production is obtained and the $b$-quark fragmentation function is inferred from the momentum spectrum of the muons. The $b$ quark is found to fragment predominantly with high values of $z$, with $〈z_b〉=0.8\mathrm{}\pm 0.1$, and to have an over-all semimuonic branching fraction of (${15.5}_{-2.9\mathrm{}}^{+5.4\mathrm{}}$)%.