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Feb12-12, 07:00 AM
P: 90
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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