Measurement of αs and the non-strange spectral functions in hadronic τ decays with OPAL

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 αs, 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 αs(mτ2) = 0.348 ± 0.009exp ± 0.019theo at the τ-mass scale and αs(m2z) = 0.1219 ± 0.0010exp ± 0.0017theo at the Z degree sign -mass scale. The values obtained for αs(m2z) using Fixed Order Perturbation Theory or Renormalon Chain Resummation are 2.3 % and 4.1 % smaller, respectively. The 'running' of the strong coupling between s0 ≅ 1.3 GeV2 and s0 = m2τ has been tested from direct fits to the integrated differential hadronic decay rate Rτ (s0). A test of the saturation of chiral sum rules at the τ-mass scale has been performed