3

In QCD, Hadrons and mesons are composed of individual particle-like excitations called quarks, that assemble in pairs and triplets of zero net color charge.

Recent questions have partially addressed the question of color moments being exactly cancelled. Although since this is an experimental observation for charges (confinement is required to explain the absence of isolated quarks), is less clear that all the moments do indeed cancel in the physical world we live in (exact cancellation of all color moments when the nucleus has no exact spherical symmetry)

The question is even less clear regarding flavor. According to the wikipedia page, flavor is just a quantum number, but is not clear to me to what extent is just a requirement of the theory for it to exist, or is just a parameter of the model to fit particle zoology.

Is the idea of a flavor field inconsistent with heavy nuclei observations?

Qmechanic
  • 220,844
UnkemptPanda
  • 361

2 Answers2

1

Color is an observation that does not translate very well to classical physics.

There's no "part" of a hadron that has any particular color more than another color, it's not like poles of magnets. The colors cancel out uniformly throughout the hadron.

Flavors are kind of like distinct objects. A muon is a muon, and an electron is an electron. The first notable difference between flavors is usually the mass. It's not really a charge it's just a different distinct thing that is similar.

Mass is not a charge, and flavors are just different mass-states that the particle can exist in, simply put. Like when electrons jump between shells, it's kind of like particles can jump between flavors.

qa test
  • 29
1

No, flavour is not a charge. In physics, the word charge is usually saved for the conserved quantities under group symmetries. Thus electric and colour charges are fundamental in the Standard Model because the entire model is built upon gauge symmetries.

That said, there is a relation between flavour and the gauge group of the Standard Model. In particular, we know that particles need to come in pairs ($u-d$, $c-s$, $t-b$ for quarks and $e-\nu_e$, $\mu-\nu_\mu$, $\tau-\nu_\tau$ for leptons). Besides that, the fact that there are three different families of particles is not a necessity of the SM but something we found from observation. Nothing prohibits adding more pairs of particles.

Regarding the idea of adding a field for the flavour quantum number, the answer is the same: fields are associated with the gauge groups of the SM, and for each gauge group we have a corresponding charge. Note that fields are not associated with the charges per se, but with the groups, so not only is there no field because flavour is not a charge, even if it was a charge, there would still be no field unless it was associated with a gauge group.

Gaussian97
  • 485