The spectral functions of the vector current and the axial-vector current have been measured in hadronic τ decays using the OPAL detector at LEP. Within the framework of the Operator Product Expansion a simultaneous determination of the strong coupling constant α s , the non-perturbative operators of dimension 6 and 8 and of the gluon condensate has been performed. Different perturbative descriptions have been compared to the data. The Contour Improved Fixed Order Perturbation Theory gives α s (m 2 τ ) = 0.348±0.009 exp ±0.019 theo at the τ -mass scale and α s (m 2 Z ) = 0.1219±0.0010 exp ±0.0017 theo at the Z 0 -mass scale. The values obtained for α s (m 2 Z ) using Fixed Order Perturbation Theory or Renormalon Chain Resummation are 2.3 % and 4.1 % smaller, respectively. The 'running' of the strong coupling between s 0 ≃ 1.3 GeV 2 and s 0 = m 2 τ has been tested from direct fits to the integrated differential hadronic decay rate R τ (s 0 ). A test of the saturation of QCD sum rules at the τ -mass scale has been performed.

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The production rates of D * ± mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary cc pairs in hadronic Z 0 decays have been measured at LEP using almost 4.4 million hadronic 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 D * ± mesons, and a bottom tag based on identified muons and electrons, the hadronisation fractions of charm and bottom quarks into D * ± mesons have been found to be f (b → D * + X) = 0.173 ± 0.016 ± 0.012 and f (c → D * + X) = 0.222 ± 0.014 ± 0.014 .The fraction of cc events in hadronic Z 0 decays, Γ cc /Γ had = Γ(Z 0 → cc)/Γ(Z 0 → hadrons), is determined to be Γ cc /Γ had = 0.180 ± 0.011 ± 0.012 ± 0.006 .In all cases the first error is statistical, and the second one systematic. The last error quoted for Γ cc /Γ had is due to external branching ratios.

We have measured the production cross-section times branching ratio for J/ψ→μ+μ- in pp̄ interactions at √s=630 GeV in the kinematic range |y| <2.0 and pT> 5 GeV/c, BR(J/ψ→μ+μ -)σ(pp̄→J/ψ)=6.18±0.24±0.81 nb. The data sample collected in 1988 and 1989 for an integrated luminosity of 4.7 pb-1 represents a fivefold improvement over the statistics in our earlier study of the J/ψ production process, and the pT distribution which is measured extends to 28 GeV/c. Using event topology we show that the rate for the direct production of J/ψ, via radiative decays of χ states, is larger than that for production via B-hadrons. Production of ψ′ is also studied using the decay modes ψ′→μ+μ- and ψ′→J/ψπ+π-