19 research outputs found
Up and down quark masses from Finite Energy QCD sum rules to five loops
The up and down quark masses are determined from an optimized QCD Finite
Energy Sum Rule (FESR) involving the correlator of axial-vector divergences, to
five loop order in Perturbative QCD (PQCD), and including leading
non-perturbative QCD and higher order quark mass corrections. This FESR is
designed to reduce considerably the systematic uncertainties arising from the
(unmeasured) hadronic resonance sector, which in this framework contributes
less than 3-4% to the quark mass. This is achieved by introducing an
integration kernel in the form of a second degree polynomial, restricted to
vanish at the peak of the two lowest lying resonances. The driving hadronic
contribution is then the pion pole, with parameters well known from experiment.
The determination is done in the framework of Contour Improved Perturbation
Theory (CIPT), which exhibits a very good convergence, leading to a remarkably
stable result in the unusually wide window , where
is the radius of the integration contour in the complex energy (squared)
plane. The results are: MeV, MeV, and Mev (at a scale Q=2 GeV).Comment: Additional references to lattice QCD results have been adde