The strange quark mass from QCD sum rules

The strange quark mass is calculated from QCD sum rules for the divergence of the vector as well as axialvector current in the next-next-to-leading logarithmic approximation. The determination for the divergence of the axial-vector current is found to be unreliable due to large uncertainties in the hadronic parametrisation of the two-point function.From the sum rule for the divergence of the vector current, we obtain a value of(1 GeV)=189±32 MeV, where the error is dominated by the unknown perturbativeO(_s³) correction. Assuming a continued geometric growth of the perturbation series, we findm_s=178±18 MeV. Using both determinations ofm_s, together with quark-mass ratios from chiral perturbation theory, we also give estimates of the light quark massesm_u andm_d.