Gluon spin and quark confinement

In summary, the conversation discusses the relationship between gluons, strong force, and the color-anticolor configuration of quarks in hadrons. It is theorized that the force between a quark and antiquark in a meson must always be attractive due to their opposite charges, while the force between three different colored quarks in a baryon could have both attractive and repulsive components. The concept of valence quarks and the role of QCD in understanding hadrons is also mentioned.
  • #1
joly
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Gluons are spin 1 particles so the Strong Force can both attract and repulse. The constituent partons of a meson are a quark and an antiquark so they must carry a given color and its anticolor, respectively, in order that there is no net color carried by the parton. In that case, the force between the quark and antiquark must be always attractive since it involves opposite type of charges. Is that reasoning correct?

If so, how does this work for a baryon, which contains 3 constituent quarks of 3 different colors? Could we have both attractive and repulsive components in the (overall attractive) confinement force, or is QCD also always attractive in that case?
 
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  • #2
Hadrons are not as easy as N quarks sitting around. The valence quarks are important, but the whole QCD mess is important as well.

The valence quarks in a hadron feel an effective attraction to the other two valence quarks as well. "Blue+red" combined is very similar to "anti-green", for example. But don't take that too literally.
 
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  • #3
mfb said:
"Blue+red" combined is very similar to "anti-green"

Doesn't blue+red combined exactly give anti-green? (I'm asking this because you wrote similar)
 
  • #4
Thank you. I was thinking of the heavy (static) quark, quenched, approximation that is e.g. studied by lattice QCD. This is a simple case to picture the confinement mechanism, although as you say it does not contains the full story: the QCD string appears to break down when light quark pair-creation is allowed. Nevertheless, it seems educative to consider the static quenched approximation even if it is not fully QCD. In that case, I suppose that the valence quark picture should be reasonable. If so, does the reasoning based on the color-anticolor configuration of the q-qbar pair leading to an always attractive force makes sense?

For the baryons, blue+red=anti-green seems to be a good answer. It reminds of the quark-diquark picture.
 
  • #5
Garlic said:
Doesn't blue+red combined exactly give anti-green? (I'm asking this because you wrote similar)
If you add the colors, yes, but you have two different valence quarks with those colors, not a single anti-green valence quark.
joly said:
If so, does the reasoning based on the color-anticolor configuration of the q-qbar pair leading to an always attractive force makes sense?
Yes.
 
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1. What are gluon spins and how do they affect quark confinement?

Gluon spins refer to the intrinsic angular momentum of gluons, which are the carriers of the strong nuclear force. Quark confinement is a phenomenon where quarks are always confined within particles and cannot exist as isolated particles. Gluon spins play a crucial role in quark confinement by mediating the strong force between quarks and binding them together in particles.

2. How are gluon spins measured?

Gluon spins can be indirectly measured through experiments that study the properties of particles that contain quarks, such as protons and neutrons. These experiments involve colliding particles and analyzing the patterns of particles produced in order to determine the spin of gluons.

3. What is the relationship between gluon spin and the strong nuclear force?

The strong nuclear force is the strongest of the four fundamental forces in the universe and is responsible for binding quarks together to form particles. Gluon spins are a fundamental property of gluons and they play a crucial role in mediating the strong force between quarks.

4. Can gluon spins change?

Yes, gluon spins can change through a process called spin-flipping, where a gluon's spin can be flipped to the opposite direction. This process can occur during particle interactions and can impact the properties of the particles involved.

5. How does the study of gluon spins and quark confinement contribute to our understanding of the universe?

The study of gluon spins and quark confinement is an important aspect of understanding the fundamental forces and particles that make up our universe. It also helps us to understand the properties and behavior of matter at a subatomic level, which has implications for fields such as particle physics, astrophysics, and nuclear physics.

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