2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 4, 557-570
DOI 10.1007/s100529800939

Measurement of the fraction
of hadronic Z decays into charm quark pairs

The ALEPH Collaboration
R. Barate - et al.

Laboratoire de Physique des Particules (LAPP), IN2P3-CNRS, F-74019 Annecy-le-Vieux Cedex, France

Received: 6 March 1998 / Published online: 2 July 1998

The full statistics of hadronic Z decays collected with the ALEPH detector are analysed to measure, by three methods, the ratio, ${\rm R_c}$, of the partial decay width of the Z into ${\rm c\bar{c}}$ quarks to the total hadronic width. One method uses the inclusive p and $p_{\perp}$ spectra of electrons. The other two use a double-tagging technique to measure ${\rm R_c}$ independently of the charm-tagging efficiency. In one, the tagging procedure uses the reconstruction of high momentum charmed mesons (${\rm D^{*+}}$, ${\rm D^+}$ and ${\rm D^0}$) to detect the charm quarks. In the other, a charm quark is tagged from the ${\rm D^*}$'s reconstructed in the ${\rm D^{*+} \to \pi^+ D^0}$ decay channel and the other from the slow pion from the ${\rm D^{*-} \to \pi^-
 \bar{D}^0}$ decay. The combination of these measurements leads to ${\rm R_c = \Gamma(Z \to c\bar{c}) / \Gamma(Z \to hadrons)}) =
 0.1681\pm0.0054({\rm stat})\pm0.0062({\rm syst})$.

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