Weak force and axial vector coupling

  • Thread starter a dull boy
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  • #1
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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
 

Answers and Replies

  • #2
Vanadium 50
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Only the term with the gamma_5 in it contributes.
 
  • #3
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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
 
  • #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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