GlueX Physics Quark Model

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GlueX Physics

Quark Model

Mesons in the Quark Model

To do this, I want to start with the very basics of the strong interaction, namely the conserved quantities, J, P, C, ···. With this, I want to look at spectroscopy within one specific model, the constituent quark model. This model is by no means perfect. It provides no explanation for confinement, and the role of gluons is not obvious. It also makes no absolute mass predictions, and no absolute rate predictions for decays. However it does make a rather large number of very good predictions. It also provides a very natural framework within which to classify mesons. It provides a natural handle to address issues such as structure and decays, and even makes some rather nice predictions for relative decay rates.

The strong interaction conserves a number of quantities, some of which are listed here.
B Baryon number.
Q Electric charge.
J Angular momentum.
S Strangeness.
I Strong isospin.
P Parity.
C Charge conjugation.
G G–parity.
Those that are used will be explained as we go along. However, a number of these are carried by the quarks themselves. In table 1 are given the quantum numbers of the three lightest quarks.








Table 1: Quantum numbers of the quarks. B is baryon number, Q is electric charge, J is the spin, S is strangeness, I is the strong isospin and Iz is the projection of I along the quantization axis, (usually defined as z).

In the constituent quark model, we treat a meson as a bound quark-antiquark pair, qq ̄, and then draw an analogy to the positronium system, e+e− to understand what we are seeing. In this picture the q and the q ̄ both have spin 1 . These can combine 2 to either total spin S = 0, or total spin S = 1.

Review Papers

Exotic Quantum Number Mesons

Lattice QCD Calculations


== Strong Decay Models==