QCD SUM-RULES FOR THE ISOSPIN-BREAKING AXIAL CORRELATOR WITH CORRECT CHIRAL BEHAVIOR

We revisit the QCD sum-rule treatment of the isospin-breaking correlat or [0\T[A(mu)(3)(x)A(nu)(8)(0)]\0], in light of the recent claim that a previous treatment produced results incompatible with known chiral c onstraints. The source of the error in the previous analysis is identi fied, and a corrected version of the sum-rule treatment obtained. It i s then shown that, using input from chiral perturbation theory, one ma y use the resulting sum rule to extract information on the leading chi ral behavior of isospin-breaking parameters associated with the coupli ng of excited pseudoscalar resonances to the axial currents. A rather accurate extraction is possible for the case of the eta'. Demanding st ability of the sum-rule analysis also allows us to improve the upper b ound on the fourth-order low-energy constant, L-7.