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SUMMARY:Up- and Down- Quark Masses from QCD Finite Energy Sum Rules
DTSTART;VALUE=DATE-TIME:20181204T152000Z
DTEND;VALUE=DATE-TIME:20181204T154000Z
DTSTAMP;VALUE=DATE-TIME:20260912T075008Z
UID:indico-contribution-1169@indico.tlabs.ac.za
DESCRIPTION:Speakers: Alexes Mes (University of Cape Town)\nDue to quark-g
 luon confinement in QCD\, the quark masses entering the QCD Lagrangian can
 not be measured directly like\, for example\, the electron or the proton m
 ass. They must be determined either numerically from Lattice QCD\, or anal
 ytically using QCD sum rules. The latter makes use of the complex squared 
 energy plane\, and Cauchy’s theorem for the current-current correlator o
 f the axial-vector divergences. This procedure relates a QCD expression co
 ntaining the quark masses\, with a hadronic expression in terms of known h
 adron masses\, couplings\, and lifetimes/widths. Thus\, the quark masses b
 ecome a function of known hadronic information. \nWe determine the up- and
  down- quark masses from a QCD Finite Energy Sum Rule\, using the pseudosc
 alar correlator to six-loop order in perturbative QCD\, with the leading v
 acuum condensates and higher order quark mass corrections included. We red
 uce the systematic uncertainties stemming from the hadronic resonance sect
 or by introducing an integration kernel in the Cauchy integral in the comp
 lex squared energy plane. Further\, we examine the issue of convergence of
  the perturbative QCD expression of the pseudoscalar-current correlator. B
 oth the Fixed Order Perturbation Theory (FOPT) method and Contour Improved
  Perturbation Theory (CIPT) method are explored. Our results from the latt
 er exhibit very good convergence and stability in the wide window s$_0$ = 
 1.5 − 4.0 GeV$^2$\, where s$_0$ is the radius of the integration contour
  in the complex squared energy s-plane. The results are: (m$_u$ +m$_d$)/2 
 = 4.36 ± 0.36 MeV (at a scale Q = 2 GeV)\, m$_u$(Q = 2 GeV) = 2.83 ± 0.2
 3 MeV\, and m$_d$(Q = 2 GeV) = 5.90 ± 0.48  MeV.\n\nhttps://indico.tlabs.
 ac.za/event/75/contributions/1169/
LOCATION:Casa do Sol
URL:https://indico.tlabs.ac.za/event/75/contributions/1169/
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