QCD Coulomb Singularity: Quarkonium w/ 2 Gluons

In summary, the conversation discusses the Coulomb singularity in QCD, which appears when a virtual gluon is exchanged between a quark pair in a meson. It is generated when the relative velocity of the quarks approaches zero, and the expression for this singularity is ~ 1/v. This phenomenon is not present in QED. The discussion also mentions NRQCD as a relevant model and provides a reference for further reading.
  • #1
mariamskhan
4
0
Hi all,
I am just new to work on NLO in QCD. I need to know how a Coulomb singularity in QCD is defined? What is the form/expression of this singularity term? Can anyone explain with an example of any Feynman diagram? I am interested in the case of a quarkonium with two gluons in final state. I'll be really grateful for the help.
 
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  • #2
Can you explain what you mean by Coulomb singularity in QED?
 
  • #3
Coulomb singularity appears whenever a virtual gluon is exchanged between quark pair of a meson. The limit that relative velocity of these two quarks tends to zero (to make a bound state for meson) in an expression ~ 1/v (v being realative velocity here) generates this singularity. This is what I know so far. I'm not sure where does this expression ~1/v come from? :cry: And with this information, I think we have Coulomb singularities only in QCD, but not in QED. :confused:
Can anybody please help or refer me to some good derivation of this? PLZZZZZZZZ
 
  • #4
I do not know about which model you are talking. QCD, low-energy effective XYZ, non-relativistic quark model, ... I have never seen 1/v in full QCD.
 
  • #5
Ooops, I really forgot to mention this. I'm talking about NRQCD.
 
  • #6
mariamskhan said:
Ooops, I really forgot to mention this. I'm talking about NRQCD.
any references? on arxiv?
 

Related to QCD Coulomb Singularity: Quarkonium w/ 2 Gluons

1. What is the QCD Coulomb Singularity?

The QCD Coulomb Singularity, also known as the Coulomb potential singularity, is a phenomenon in quantum chromodynamics (QCD) where the potential energy between two quarks becomes infinite at short distances.

2. What is Quarkonium?

Quarkonium refers to a bound state of a heavy quark and its corresponding antiquark, such as the charm quark and anti-charm quark, or bottom quark and anti-bottom quark. These particles are held together by the strong force, which is described by QCD.

3. What role do gluons play in the QCD Coulomb Singularity?

Gluons are the exchange particles of the strong force and are responsible for binding quarks together in hadrons, such as quarkonium. In the QCD Coulomb Singularity, the interaction between two gluons leads to the infinite potential energy at short distances.

4. How is the QCD Coulomb Singularity related to the confinement of quarks?

The QCD Coulomb Singularity is one of the key phenomena that contributes to the confinement of quarks. At short distances, the potential energy between quarks is infinite, making it impossible for them to exist as free particles. This is why quarks are always found bound together in hadrons.

5. What is the significance of studying QCD Coulomb Singularity in quarkonium systems?

Studying the QCD Coulomb Singularity in quarkonium systems can provide valuable insights into the nature of the strong force and the behavior of quarks at short distances. It also allows for a more comprehensive understanding of the properties and interactions of quarkonium particles.

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