Color conservation in gluon fragmentation

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Discussion Overview

The discussion revolves around the conservation of color charge during the fragmentation of gluons into quark-antiquark pairs, specifically addressing how color conservation is maintained when a colored gluon produces a colorless state in the form of a quark-antiquark pair.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that gluons carry both a color and an anticolor, suggesting that a gluon could fragment into a quark and an antiquark of different colors.
  • Others argue that when a gluon fragments into a quark and its corresponding antiquark, such as a charm quark and its antiquark, color conservation must still hold, implying specific color assignments.
  • A participant points out that the color connection to other colored objects in the hadron must be considered to understand color conservation fully.
  • Some participants emphasize that at every vertex in the interaction, color must be conserved, raising questions about how this applies to the fragmentation process.
  • One participant suggests a graphical representation of gluons and color charge conservation in QCD processes using Feynman diagrams, indicating a method to visualize the color dynamics involved.

Areas of Agreement / Disagreement

Participants express differing views on how color conservation operates during gluon fragmentation, with no consensus reached on the specifics of color assignments and the role of the surrounding hadron in the process.

Contextual Notes

The discussion highlights the complexity of color charge conservation in quantum chromodynamics (QCD) and the need to consider additional factors, such as the contributions from the rest of the hadron, which remain unresolved.

Manojg
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Hi,

When a gluon fragments to a quark anti-quark pair (c c_bar for an example), how is color conserved? Gluon is colored but c c_bar pair is colorless.

Thanks.
 
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Gluons carry both a color and an anticolor. A gluon that was red anti-green for example could fragment into a red quark and a green antiquark.
 
Bill_K said:
Gluons carry both a color and an anticolor. A gluon that was red anti-green for example could fragment into a red quark and a green antiquark.

which, since they have different color/anticolor does not form a color neutral state.
 
When the q-qbar pair fragments to hadrons, there will be a color connection to the other colored objects in the hadron that contained the original gluon.
 
Bill_K said:
Gluons carry both a color and an anticolor. A gluon that was red anti-green for example could fragment into a red quark and a green antiquark.

Yes, but we are taking about quark and its own anti-quark like c and c_bar. If c is red, c_bar must be anti-red.
 
Vanadium 50 said:
When the q-qbar pair fragments to hadrons, there will be a color connection to the other colored objects in the hadron that contained the original gluon.

Fine, but at every vetex, color (and other like charge) should be conserved, isn't it? So, at vertex where gluon fragments to c and c_bar, color should be conserved.
 
Manojg said:
Yes, but we are taking about quark and its own anti-quark like c and c_bar. If c is red, c_bar must be anti-red.


No, if the gluon splits up into a red c, the c_bar cannot be anti-red; as far as I understand.
 
Yes, but you are starting with a colored state, ignoring the rest of the hadron that gave you the gluon. It's that rest of the hadron that solves your problem. You can't ignore it.
 
There is a nice way to represent gluons and color charge conservation in QCD processes.

In a Feynman diagram replace every gluon with a double line, i.e. two antiparallel lines running into opposite direction and carrying a color charge and an anti-color charge, respectively.

http://www.hindawi.com/journals/ahep/2010/floats/723105/thumbnails/723105.fig.002_th.jpg
 

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