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Study of charm production in Z decays

  • The ALEPH Collaboration
  • R. Barate et al.
Experimental physics

Abstract.

The production rates of \({\mathrm{D}}^{*\pm}\), \({\mathrm{D}}_{\rm{s}}^{* \pm}\), \({\mathrm{D}}^{\pm}\), \({\mathrm{D}}^0 / \bar{{\mathrm{D}}}^0\), \({\mathrm{D}}_{\rm{s}}^{\pm}\), and \(\Lambda_{\rm c}^{+}/{\bar{\Lambda}}_{\rm c}^{-}\) in \({\rm Z} \rightarrow {\mathrm c} \bar{{\mathrm c}}\) decays are measured using the LEP I data sample recorded by the ALEPH detector. The fractional energy spectrum of the \({\mathrm{D}}^{*\pm}\) is well described as the sum of three contributions: charm hadronisation, b hadron decays and gluon splitting into a pair of heavy quarks. The probability for a c quark to hadronise into a \({\mathrm{D}}^{*+}\) is found to be \(f({\mathrm c} \to{\mathrm{D}}^{*+}) = 0.233 \pm 0.010 \mathrm{(stat.)} \pm 0.011\mathrm{(syst.)}\). The average fraction of the beam energy carried by \({\mathrm{D}}^{*\pm}\) mesons in \({\rm Z} \to{\rm c \bar c}\) events is measured to be \({\langle X_E ({\mathrm{D}}^{*\pm}) \rangle}_{{\mathrm c} \bar{{\mathrm c}}} =0.4878 \pm 0.0046 \mathrm{(stat.)} \pm 0.0061 \mathrm{(syst.)}.\) The \({\mathrm{D}}^{*\pm}\) energy and the hemisphere mass imbalance distributions are simultaneously used to measure the fraction of hadronic Z decays in which a gluon splits to a \({\mathrm c} \bar{{\mathrm c}}\) pair: \(\bar{n}_{\mathrm{g} \to{\mathrm c}\bar{{\mathrm c}}} = (3.23 \pm 0.48 \mathrm{(stat.)} \pm 0.53 \mathrm{(syst.)})\%.\) The ratio of the Vector/(Vector+Pseudoscalar) production rates in charmed mesons is found to be \(P_V = 0.595\pm0.045\). The fractional decay width of the Z into \({\mathrm c}\bar{{\mathrm c}}\) pairs is determined from the sum of the production rates for various weakly decaying charmed states to be \({\rm R_c} =0.1738 \pm 0.0047{\rm (stat.)} \pm 0.0116 {\rm (syst.)}.\)

Keywords

Production Rate Energy Spectrum Beam Energy Fractional Energy Heavy Quark 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • The ALEPH Collaboration
  • R. Barate et al.
    • 1
  1. 1.Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, 74019 Annecy-le-Vieux Cedex, FranceFR

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