QCD vacuum contribution to W/Z masses

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    Qcd Vacuum
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SUMMARY

The discussion centers on the contribution of the QCD vacuum condensate to the masses of the W and Z bosons, specifically addressing its role in breaking chiral symmetry and SU(2) electroweak gauge symmetry. The vacuum expectation value of the operator, which involves left-handed and right-handed quarks, is not SU(2) invariant and is estimated to contribute approximately 10 to 20 MeV to the W and Z masses. Although this effect is real, it is considered negligible in the context of electroweak precision tests (EWPT) as it acts in quadrature with the Higgs mechanism, thus having a minimal impact on the S parameter.

PREREQUISITES
  • Understanding of QCD vacuum condensates
  • Familiarity with chiral symmetry breaking in quantum chromodynamics (QCD)
  • Knowledge of SU(2) electroweak gauge symmetry
  • Basic concepts of electroweak precision tests (EWPT)
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  • Research the role of QCD vacuum condensates in particle physics
  • Study the implications of chiral symmetry breaking on mass generation
  • Examine the S and T parameters in electroweak precision tests
  • Explore the Higgs mechanism and its interactions with QCD effects
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Particle physicists, theoretical physicists, and researchers focusing on electroweak interactions and QCD effects in mass generation.

ofirg
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The QCD vacuum condensate which breaks chiral symmetry in qcd, also break the SU(2) electoweak gauge symmtery, right?
The operator which gets a vacuum expectation value isn't SU(2) invariant since it is built out of left handed quarks and right handed quarks which are in different representations of SU(2).
This should contribute about ~100MeV the W and Z masses. Why is this never taken into account in EWPT? because the condensate should be the same for up and down type quarks, I would think it woudn't contibute to the T parameter (isospin symmetry), But it should contribute to the S parameter.
Is this simply negligible, or I've got it all wrong?
 
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It is a real effect, although it's smaller than what you estimate: more like 10 or 20 MeV. It acts in quadrature with the Higgs mechanism, so the numeric effect on precision EWK is negligible.
 

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