From Hadronic τ Decays to the Chiral Couplings and

Abstract

A sum rule analysis of the hadronic τ -decay data can be used to determine the low-energy constants L r 10 (µ) and C r 87 (µ). These constants are QCD chiral-order parameters, which appear at order p 4 and p 6 , respectively, in the chiral perturbation theory expansion of the V −A correlator. At order p 4 we obtain L r 10 (Mρ) = −(5.22±0.06)·10 −3 . Including in the analysis the order p 6 contributions, we get L r 10 (Mρ) = −(4.06 ± 0.39) · 10 −3 and C r 87 (Mρ) = (4.89 ± 0.19) · 10 −3 GeV −2 .