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Weak force coupling to left-handed particles

  1. Apr 23, 2013 #1
    The W couples to left-handed particles only. What about the Z? Is it the same?

    Thanks in advance!
  2. jcsd
  3. Apr 23, 2013 #2


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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.
  4. Apr 23, 2013 #3
    Thanks for a thorough answer!
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