A The vertex factors in QCD penguin operators

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The discussion centers on the presence of a (V+A) term in QCD penguin operators, specifically in O5 and O6. Participants question why this term exists when electroweak theory typically assigns a (V-A) factor to Dirac spinor-W boson vertices, as W bosons couple only to left Weyl spinors. The conversation highlights the need for clarity on what is being calculated to understand the inclusion of the (V+A) term. One participant acknowledges the confusion but later expresses that the issue is now clear. The dialogue emphasizes the importance of context in theoretical calculations.
Elmo
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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 ?
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Elmo said:
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.
 
Vanadium 50 said:
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.
 

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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.
 
Vanadium 50 said:
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.
 
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