Implications of the ALEPH tau-Lepton Decay Data for Perturbative and
Non-Perturbative QCD
release_k4fvdw3i5zfm5jvc5vy2f72ski
by
Thomas Schaefer,
Edward Shuryak (Stony
Brook)
2000
Abstract
We use ALEPH data on hadronic τ decays in order to calculate Euclidean
coordinate space correlation functions in the vector and axial-vector channels.
The linear combination V-A receives no perturbative contribution and is
quantitatively reproduced by the instanton liquid model. In the case of V+A
the instanton calculation is in good agreement with the data once perturbative
corrections are included. These corrections clearly show the evolution of
α_s. We also analyze the range of validity of the Operator Product
Expansion (OPE). In the V-A channel we find a dimension d=6 contribution
which is comparable to the original SVZ estimate, but the instanton model
provides a different non-singular term of the same magnitude. In the V+A case
both the OPE and the instanton model predict the same d=4 power correction
induced by the gluon condensate, but it is masked by much larger perturbative
contributions. We conclude that the range of validity of the OPE is limited to
x0.3 fm, whereas the instanton model describes the data over the entire
range.
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