Weak force and axial vector coupling

  • Thread starter a dull boy
  • Start date
  • #1
40
1

Main Question or Discussion Point

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
Staff Emeritus
Science Advisor
Education Advisor
2019 Award
24,017
6,572
Only the term with the gamma_5 in it contributes.
 
  • #3
40
1
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
Science Advisor
Insights Author
4,155
194
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.
 

Related Threads on Weak force and axial vector coupling

Replies
1
Views
280
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
546
Replies
5
Views
5K
  • Last Post
Replies
1
Views
393
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
3
Views
608
Replies
13
Views
1K
Replies
1
Views
3K
Replies
3
Views
593
Top