Do Quarks Emit Photons Like Gluons?

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Discussion Overview

The discussion revolves around the role of photons and gluons in quark interactions, specifically whether quarks can emit photons in a manner analogous to gluons. Participants explore the theoretical implications of such processes, including conservation laws and the conditions under which these emissions might occur.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a photon can play a similar role to a gluon in quark-level diagrams, considering the color-neutrality of gluons.
  • Another participant asserts that quark-antiquark annihilation can produce photons, albeit with lower probability than gluons, and notes that quarks interact with photons due to their electric charge.
  • A participant seeks clarification on a specific process where a single quark emits a photon, which then decays into two quarks.
  • One response indicates that the photon can be viewed as a "long distance effect" compared to the "short distance" effect of gluons, and provides a diagrammatic representation of possible interactions.
  • A later reply corrects an earlier assumption about color neutrality, stating that quarks do not emit color-neutral photons while retaining their color charge.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and conditions of quarks emitting photons, with some supporting the idea while others challenge specific aspects of the proposed processes. The discussion remains unresolved regarding the specifics of photon emission by quarks.

Contextual Notes

There are limitations regarding the assumptions about color charge and the conditions under which photons can be emitted or involved in quark interactions. The discussion does not resolve the complexities of these interactions.

copernicus1
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In quark-level diagrams of decays, I often see, for instance, a baryon with one quark emitting a gluon and then the gluon goes on to decay into two new quarks. What I'm wondering is, if the gluon is color-neutral, can a photon play this same role in theory? Is this impossible due to some conservation law or other principle, or just very unlikely?

Thanks!
 
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Yes, quark-antiquark annihilation can produce photons (though with lower probability than gluons) and quark-quark and quark-antiquark scattering can be mediated by photon exchange. Quarks are electrically charged which is enough to tell you they interact with photons.

Edit: Though note that quark-antiquark annihilation into photons can only occur if the incoming particles have the same flavour and are anti-colour pairs. So a blue up quark can annihilate with an anti-blue up antiquark into photons.
 
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Hmm well I know that two quarks can annihilate to produce photons, but I guess I'm wondering about a more specific process here---where a single quark emits a photon, so that the original quark and the photon both go flying off, and then the photon decays into two quarks.
 
Yes, its possible. The photon can be considered a "long distance effect" while the strong a "short distance" effect. (all about energy scales).

Here are the first order diagrams for an up going to an up and a down-antidown pair:

[tex] \left(<br /> \begin{array}<br /> \text{WEAK} & \text{PHOTON}\\<br /> \text{GLUON} & \text{Z BOSON}<br /> \end{array}\right)[/tex]

nf3b5x.jpg
 
Wow thanks!
 
Just one detail:
copernicus1 said:
What I'm wondering is, if the gluon is color-neutral
There are no color-neutral quarks.
If a quark emits a photon, it simply keeps its color charge.
 

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