On the QCD sum rule determination of the strange quark mass

In the QCD sum rule determination of ms using the two-point correlator of divergences of ΔS = 1 vector currents, the final uncertainty on ms is mainly due to the hadronic spectral function. Using a specific parameterization which fully takes into account the available experimental data on the Kπ (I = 12, JP = 0+ system, characterized by the presence of a relevant nonresonant component in addition to the resonant one, we find ms(1 GeV) ⩾ 120 MeV. In particular, varying only the parameters describing the nonresonant Kπ component and ΛMSnf=3 we obtain ms(1 GeV) = 125–160 MeV. This result is smaller than analogous ones obtained by using a parameterization in terms of only resonant states. We discuss how to systematically improve the determination of ms by this method.