Measurement of ${\rm f(c \to D^{*+} X)}$, ${\rm f(b \to D^{*+} X)}$ and $\Gamma_{\rm c\bar c}/\Gamma_{\rm had}$ using ${\rm D}^{*\pm}$ mesons

Abstract.

The production rates of ${\rm D}^{*\pm}$ mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary ${\rm c\bar c}$ pairs in hadronic ${\rm Z}^0$ decays have been measured at LEP using almost 4.4 million hadronic ${\rm Z}^0$ decays collected with the OPAL detector between 1990 and 1995. Using a combination of several charm quark tagging methods based on fully and partially reconstructed ${\rm D}^{*\pm}$ mesons, and a bottom tag based on identified muons and electrons, the hadronisation fractions of charm and bottom quarks into ${\rm D}^{*\pm}$ mesons have been found to be \[ {\rm f(b \to D^{*+}}X) = 0.173 \pm 0.016 \pm 0.012\quad {\rm and }\quad {\rm f (c \to D^{*+}}X) = 0.222 \pm 0.014 \pm 0.014\; . \] The fraction of ${\rm c\bar c}$ events in hadronic ${\rm Z}^0$ decays, $\Gamma_{\rm c\bar c}/\Gamma_{\rm had}=\Gamma({\rm Z}^0\to{\rm c\bar c}) / \Gamma({\rm Z}^0\to\rm hadrons)$, is determined to be \[ \Gamma_{\rm c\bar c}/\Gamma_{\rm had} = 0.180\pm 0.011 \pm 0.012 \pm 0.006 \ . \] In all cases the first error is statistical, and the second one systematic. The last error quoted for $\Gamma_{\rm c\bar c}/\Gamma_{\rm had}$ is due to external branching ratios.