Strange Quark, Tachyonic Gluon Masses and V_{us} from Hadronic Tau Decays

Abstract

We apply, to the new OPAL data on V+A strange spectral functions, a suitable combination of QCD spectral sum rules directly sensitive to the combination of strange quark (m_s) and tachyonic gluon (λ^2) masses . Using the mean value of λ^2 from a sum rule analysis of different channels, we deduce the invariant strange quark mass m_s= (106 +33 -37) MeV to order α_s^3, which leads to the running mass m_s(2 GeV)= (93 +29 -32) MeV. We also obtain an interesting though less competitive estimate of the CKM angle: |V_{us}|=0.217\pm 0.019.