Can a quark emit a photon

In summary, the conversation discusses the possibility of a photon playing the same role as a gluon in quark-level diagrams of decay. It is mentioned that while quark-antiquark annihilation can produce photons, it is more likely to be mediated by gluons. However, it is also possible for a single quark to emit a photon, with the original quark and the photon both flying off and the photon subsequently decaying into two new quarks. This process is described as a "long distance effect" compared to the "short distance" effect of strong interactions. It is also noted that there are no color-neutral quarks and if a quark emits a photon, it retains its color charge.
  • #1
copernicus1
99
0
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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  • #2
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.
 
Last edited:
  • #3
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.
 
  • #4
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(
\begin{array}
\text{WEAK} & \text{PHOTON}\\
\text{GLUON} & \text{Z BOSON}
\end{array}\right)
[/tex]

nf3b5x.jpg
 
  • #5
Wow thanks!
 
  • #6
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.
 

1. Can a quark emit a photon?

Yes, a quark can emit a photon. In fact, all charged particles have the ability to emit photons.

2. How does a quark emit a photon?

A quark emits a photon through a process called bremsstrahlung radiation, where the quark is accelerated and changes direction, causing it to emit a photon.

3. Can a quark emit multiple photons?

Yes, a quark can emit multiple photons. The number of photons emitted is dependent on the energy of the quark and the strength of its interaction with other particles.

4. What is the significance of a quark emitting a photon?

A quark emitting a photon helps us understand the fundamental interactions between particles and how they interact with each other through the exchange of photons.

5. Can a quark emit a photon without interacting with other particles?

No, a quark cannot emit a photon without interacting with other particles. According to the law of conservation of energy, the energy of the photon emitted must come from the energy of the quark, which can only happen through an interaction with another particle.

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