QCD vacuum condensates from tau-lepton decay data

The QCD vacuum condensates in the Operator Product Expansion are extractedfrom the final ALEPH data on vector and axial-vector spectral functions from$\tau$-decay. Weighted Finite Energy Sum Rules are employed in the framework ofboth Fixed Order and Contour Improved Perturbation Theory. An overallconsistent picture satisfying chirality constraints can be achieved only forvalues of the QCD scale below some critical value $\Lambda\simeq350 {MeV}$. Forlarger values of $\Lambda$, perturbation theory overwhelms the powercorrections. A strong correlation is then found between $\Lambda$ and theresulting values of the condensates. Reasonable accuracy is obtained up todimension $d=8$, beyond which no meaningful extraction is possible.Comment: Revised version: minor explanatory sentences added. No change in results nor figure