QCD, a part of standard model?

In summary, QCD is indeed a part/sector of the standard model of particle physics. Quarks experience both the electromagnetic and weak forces, and the Salam-Weinberg unified Electroweak force acts on them. While it is sometimes possible to consider QCD or its first flavor in isolation, this does not negate the existence of other forces such as beta decay. The experimental data also supports the inclusion of SU(3) in the standard model.
  • #1
BuckeyePhysicist
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How is it not an exactly accurate understanding that QCD is a part/sector of the standard model of particle physics ? Or, it actually is?
 
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  • #2
BuckeyePhysicist said:
How is it not an exactly accurate understanding that QCD is a part/sector of the standard model of particle physics ? Or, it actually is?


It is. Quarks feel both the elecromagnetic force (they're electrically charged) and the weak force (they change identities, manifesting weak decay, and emitting both weak bosons and leptons), and the Salam-Weinberg unified Electroweak force therefore acts on them. Because these events are weak compared to the strong (color) force, it is sometimes permissible and possible to consider the QCD model, or even its first flavor (up and down quarks and their antiparticles) in isolation, but this is in no way intended to imply that for example, beta decay doesn't exist!
 
  • #3
Moreover, the experimental fitting of scattering amplitudes gets its right value if we have a multiplicity three for the quarks. So definitively SU(3) is included in the standard model.
 

1. What is QCD?

Quantum Chromodynamics (QCD) is a theory that describes the strong interaction, one of the four fundamental forces of nature. It is a part of the Standard Model of particle physics and explains how quarks and gluons interact with each other to form composite particles such as protons and neutrons.

2. What are quarks and gluons?

Quarks are elementary particles that make up protons, neutrons, and other hadrons. They have a fractional electric charge and come in six different flavors: up, down, charm, strange, top, and bottom. Gluons are particles that mediate the strong force between quarks. They carry the color charge, which is the property that allows quarks to interact with each other via the strong force.

3. How does QCD explain the behavior of quarks and gluons?

QCD is based on the principles of quantum mechanics and special relativity. It describes how quarks and gluons interact with each other through the exchange of virtual gluons. The theory also explains the confinement of quarks, which means that they cannot exist as free particles but are always bound together to form composite particles.

4. Why is QCD important?

QCD is a crucial part of the Standard Model of particle physics, which is the most successful theory we have for understanding the fundamental building blocks of the universe. It has been extensively tested and has accurately predicted the results of many experiments. QCD also helps us understand the behavior of matter in extreme conditions, such as in the early universe or inside neutron stars.

5. What are the remaining challenges in understanding QCD?

Although QCD is a well-established theory, there are still some unanswered questions, such as the nature of confinement and the mass of quarks. Another challenge is to reconcile QCD with gravity, which is described by the theory of general relativity. Scientists are also trying to use QCD to understand the properties of exotic particles, such as quark-gluon plasma, which is believed to have existed in the early universe.

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