K. Ackerstaff et al., Measurement of the strong coupling constant alpha(s) and the vector and axial-vector spectral functions in hadronic tau decays, EUR PHY J C, 7(4), 1999, pp. 571-593
The spectral functions of the vector current and the axial-vector current h
ave been measured in hadronic tau decays using the OPAL detector at LEP. Wi
thin the framework of the Operator Product Expansion a simultaneous determi
nation of the strong coupling constant or,, the non-perturbative operators
of dimension 6 and 8 and of the gluon condensate has been performed. Differ
ent perturbative descriptions have been compared to the data. The Contour I
mproved Fixed Order Perturbation Theory gives alpha(s)(m(tau)(2)) = 0.348 /- 0.009(exp) +/- 0.019(theo) at the tau-mass scale and alpha(s)(m(Z)(2)) =
0.1219 +/- 0.0010(exp) +/- 0.0017(the)o at the Z(0)-mass scale. The values
obtained for alpha(s)(m(Z)(2)) using Fixed Order Perturbation Theory or Re
normalon Chain Resummation are 2.3% and 4.1% smaller, respectively. The 'ru
nning' of the strong coupling between s(0) similar or equal to 1.3 GeV2 and
s(0) = m(tau)(2) has been tested from direct fits to the integrated differ
ential hadronic decay rate R-tau(s(0)). A test of the saturation of QCD sum
rules at the tau-mass scale has been performed.