PRODUCTION AND DECAY OF CHARMED MESONS AT THE Z-RESONANCE

In a sample of 190 000 hadronic Z decays, three signals of charm production are observed: two from the exclusive decays D0 --> K-pi+ and D*+ --> D0-pi+ --> K-pi+pi+ and one in the transverse-momentum distribution of soft hadrons relative to the nearest jet. The features of these signals are in good agreement with expectations based on the standard model and previous measurements of the branching fractions. The number of D* +/- --> K -/+ pi +/- pi +/- per hadronic decay of the Z is measured to be (5.11 +/- 0.34) x 10(-3), and the branching ratio B(D0 --> K-pi+) is (3.62 +/- 0.34 +/- 0.44)%. Charm hadronization has been studied. The average fraction of the beam energy carried by the D* meson is found to be <X(E)>c = 0.504(-0.017)+0.013 +/- 0.008, and implications of the measurements on the pseudoscalar-to-vector production ratio of charmed mesons are discussed.