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Weak force and axial vector coupling

  1. Oct 26, 2011 #1
    Hi physics forum,

    I have been reading David Griffith's book "intro to elementary particles" and he
    describes the decay of the pi-meson as "pure axial vector"

    Can someone tell me what this means, in terms of the weak force vertex consisting of
    this factor

    γu(1-γ5)

    Thanks, Mark
     
  2. jcsd
  3. Oct 26, 2011 #2

    Vanadium 50

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    Only the term with the gamma_5 in it contributes.
     
  4. Oct 26, 2011 #3
    Thanks for the reply. I'll follow up 1) what does that mean physically, for example, do only certain particle types engage in pure axial coupling? 2) can you say a little as how
    the math would work (how can the vector part of V-A not contribute, since the axial
    part is multiplied by the vector (γuγ5

    I am a novice in this, so it may not be a good question! -Mark
     
  5. Oct 26, 2011 #4

    Bill_K

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    db, The weak interaction is an interaction between weak currents, JμJμ. For the lepton pair the particles are free, and Jμ is of the V-A form.

    However the quarks that make up the pion are not free, they are in a bound pseudoscalar state. You can combine their wavefunction with the 4-momentum kμ to construct an axial vector current, but there is no way to make a vector current.
     
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