Strange quark condensate from QCD sum rules to five loops

Abstract

It is argued that it is valid to use QCD sum rules to determine the scalar and pseudoscalar two-point functions at zero momentum, which in turn determine the ratio of the strange to non-strange quark condensates $R_{su}=\frac{<\bar{s}s>}{<\bar{q}q>}$ with ($q=u,d$). This is done in the framework of a new set of QCD Finite Energy Sum Rules (FESR) that involve as integration kernel a second degree polynomial, tuned to reduce considerably the systematic uncertainties in the hadronic spectral functions. As a result, the parameters limiting the precision of this determination are ${\Lambda }_{QCD}$, and to a major extent the strange quark mass. From the positivity of $R_{su}$ there follows an upper bound on the latter: $\overline{m_s}(2GeV)\le 121(105)MeV$, for ${\Lambda }_{QCD}=330(420)MeV.$

Comments: Minor changes to Sections 2 and 6