Light-quark vacuum condensates in chiral perturbation theory and QCD sum rules

Abstract

The (simplified) relation ( 〈 uu〉 − 〈 dd〉)/(〈 uu〉 − 〈 ss〉) = (m d− m u)/(m s−m u) , originally obtained in chiral perturbation theory, relating light quark masses and condensates is rederived in the context of QCD or SVZ sum rules, thus establishing a non-trivial connection between the role played by meson resonances in these two QCD-inspired approaches. Accurate values for light quark condensates deduced from scalar QCD sum rules are also presented.