The strange-quark mass from QCD sum rules in the pseudoscalar channel

QCD Laplace transform sum rules, involving the axial-vector current divergences, are used in order to determine the strange quark mass. The two-point function is known in QCD up to four loops in perturbation theory, and up to dimension-six in the non-perturbative sector. The hadronic spectral function is reconstructed using threshold normalization from chiral symmetry, together with experimental data for the two radial excitations of the kaon. The result for the running strange quark mass, in the $\overline{MS}$ scheme at a scale of 1 ${GeV}^2$ is: ${\bar{m}}_s(1Ge{V}^2)=155\pm 25MeV$.