Weak force coupling to left-handed particles

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SUMMARY

The discussion clarifies the coupling characteristics of the W and Z bosons to left-handed particles. The W boson exclusively couples to left-handed particles with the coupling defined as -i(g/√2)½γμ(1 - γ5). In contrast, the Z boson couples to both left-handed and right-handed particles, with its coupling expressed as -i(g/cos θW)½γμ(cV - cAγ5). Specific values for the couplings of various fermions, such as electrons and quarks, are provided, highlighting the differences in their coupling constants.

PREREQUISITES
  • Understanding of weak force interactions in particle physics
  • Familiarity with the Standard Model of particle physics
  • Knowledge of fermion properties, including weak isospin and charge
  • Basic grasp of quantum field theory and gamma matrices
NEXT STEPS
  • Study the derivation of the W and Z boson coupling equations in detail
  • Explore the implications of weak isospin in particle interactions
  • Investigate the role of the Higgs mechanism in mass generation for W and Z bosons
  • Learn about the experimental verification of weak force couplings through particle collision data
USEFUL FOR

Particle physicists, students of quantum field theory, and researchers focusing on the Standard Model and weak interactions will benefit from this discussion.

JoePhysicsNut
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The W couples to left-handed particles only. What about the Z? Is it the same?

Thanks in advance!
 
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The Z couples to both. Quoting from Halzen and Martin, the W coupling is -i(g/√2)½γμ(1 - γ5), which is left-hand only. By contrast, the Z coupling is -i(g/cos θW)½γμ(cV - cAγ5) where cV = T3 - 2 sin2θWQ and cA = T3.
T3 is the weak isospin of the fermion in question and Q is its charge.
For e-, μ- the values are cA = -1/2, cV = -0.03.
For u, c quarks, cA = 1/2, cV = 0.19.
For d, s quarks, cA = -1/2, cV = -0.34.
 
Bill_K said:
The Z couples to both. Quoting from Halzen and Martin, the W coupling is -i(g/√2)½γμ(1 - γ5), which is left-hand only. By contrast, the Z coupling is -i(g/cos θW)½γμ(cV - cAγ5) where cV = T3 - 2 sin2θWQ and cA = T3.
T3 is the weak isospin of the fermion in question and Q is its charge.
For e-, μ- the values are cA = -1/2, cV = -0.03.
For u, c quarks, cA = 1/2, cV = 0.19.
For d, s quarks, cA = -1/2, cV = -0.34.

Thanks for a thorough answer!
 

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