The vertex factors in QCD penguin operators

In summary, (V+A) is included in Eqtns(5.4) as part of the projection operator for the right Weyl from a Dirac spinor. According to the Feynman rules of electroweak theory, there is a (V-A) assigned to each (Dirac) spinor-W boson vertex, but in penguin diagrams with a quark-antiquark loop coupling to the W, both vertices may have the same (V-A) factor. However, if the goal is to put constraints on a potential V+A interaction or component, it is necessary for it to be included.
  • #1
Elmo
35
6
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 ?
Screenshot (51).png
 
Physics news on Phys.org
  • #2
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.
 
  • Like
Likes Elmo
  • #3
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.
 

Attachments

  • Screenshot (53).png
    Screenshot (53).png
    51.5 KB · Views: 133
  • Screenshot (54).png
    Screenshot (54).png
    43.5 KB · Views: 139
  • Screenshot (55).png
    Screenshot (55).png
    40 KB · Views: 119
  • #4
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.
 
  • #5
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.
 

1. What are vertex factors in QCD penguin operators?

Vertex factors refer to the coefficients that appear in the Feynman diagrams of QCD penguin operators. These operators are used to describe the interactions between quarks and gluons in quantum chromodynamics (QCD). The vertex factors represent the strength of the interaction between the particles involved in the process.

2. How are vertex factors calculated in QCD penguin operators?

Vertex factors are calculated using a combination of theoretical calculations and experimental data. Theoretical calculations involve using mathematical equations and models to predict the values of the vertex factors. Experimental data, obtained from particle collider experiments, is used to verify and refine these calculations.

3. What is the significance of vertex factors in QCD penguin operators?

Vertex factors play a crucial role in understanding the behavior of quarks and gluons in QCD interactions. They provide important information about the strength and nature of these interactions, which is essential for predicting and interpreting the results of particle collider experiments.

4. How do vertex factors in QCD penguin operators affect the Standard Model of particle physics?

The Standard Model of particle physics is a theory that describes the fundamental particles and their interactions. Vertex factors in QCD penguin operators are a key component of this model as they help to explain the behavior of quarks and gluons. Any discrepancies between the predicted and observed values of these factors could indicate the need for a new theory beyond the Standard Model.

5. Are there any current research developments related to vertex factors in QCD penguin operators?

Yes, there is ongoing research in this area to improve the accuracy of theoretical calculations and to obtain more precise experimental data. Additionally, there are efforts to extend the study of vertex factors to other types of interactions, such as electroweak interactions, to gain a more complete understanding of the fundamental forces in nature.

Similar threads

A The Factorization Theorem in Particle Physics
    • High Energy, Nuclear, Particle Physics
Replies
6
Views
1K
A Operator Product Expansion as shown in Schwartz
    • High Energy, Nuclear, Particle Physics
Replies
4
Views
1K
A Two loop Feynman diagram with quartic vertex
    • High Energy, Nuclear, Particle Physics
Replies
1
Views
1K
A How to deal with colour indices on spinors
    • High Energy, Nuclear, Particle Physics
Replies
1
Views
1K
A How the g factor comes from QFT?
    • High Energy, Nuclear, Particle Physics
Replies
1
Views
2K
New properties of "standard model effective field theory"
    • Beyond the Standard Models
Replies
7
Views
2K
I Muon g-2 as a constraint on new physics
    • Beyond the Standard Models
Replies
18
Views
3K
What is the Role and Significance of Feynman Diagrams in Quantum Physics?
    • Other Physics Topics
Replies
1
Views
1K
Conformal field theory: vertex operator
    • Quantum Physics
Replies
11
Views
3K
The Standard Model and Beyond
    • Science and Math Textbooks
Replies
1
Views
4K

Hot Threads

Recent Insights

Back
Top