A combination of finite energy sum rule techniques and Chiral Perturbation Theory (ChPT) is used in order to exploit recent ALEPH data on the non-strange tau vector (V) and axial-vector (A) spectral functions with respect to an experimental determination of the ChPT quantity L_{ 10}. A constrained fit of R_{ \tau,V-A}^(k,l) inverse moments (l<0) and positive spectral moments (l>=0) adjusts simultaneously L_{ 10} and the nonperturbative power terms of the Operator Product Expansion. We give explicit formulae for the first k=0,1 and l=-1,-2 strange and non-strange inverse moment chiral sum rules to one-loop order generalized ChPT. Our final result reads L^r_{ 10}(M_\rho)=-(5.13 +/- 0.19)x10^{ -3}, where the error includes experimental and theoretical uncertainties.
Categories: hep-ph hep-ex