The vertex factors in QCD penguin operators

[Elmo]

TL;DR Summary

Not sure why there is a (V+A) term in here.

Have a look at O5 & O6 in Eqtns(5.4) . Why is there a (V+A) ?
(V+A) contains the projection operator which projects out the right Weyl from a Dirac spinor.
As per the Feynman rules of electroweak theory, there is a (V-A) assigned to each (Dirac) spinor-W boson vertex because W only couple to left Weyl spinors.
In the corresponding penguin diagrams there is the quark-antiquark loop coupling to the W so shouldn't both vertices have the same (V-A) factor always ?

 

[Vanadium 50]

Summary:: Not sure why there is a (V+A) term in here.

so shouldn't both vertices have the same (V-A) factor always ?

Maybe. You didn't post enough for us to see what is being calculated. We therefore can't tell what should or should not be there.

 

[Elmo]

Maybe. You didn't post enough for us to see what is being calculated. We therefore can't tell what should or should not be there.

oh sorry.np Here it is.

 

[Vanadium 50]

You still haven't shown us what is being calculated. Why this slow drip...drip..drip of information?

If the goal is, for example, to put constraints on a potential V+A interaction or component, of course it needs to be there.

 

[Elmo]

You still haven't shown us what is being calculated. Why this slow drip...drip..drip of information?

If the goal is, for example, to put constraints on a potential V+A interaction or component, of course it needs to be there.

oh actually no,I think its all clear now.
Sorry for bugging ye all.
Thanks anyway.