An introduction to the quark model

Few-charge systems History of the quark model Mesons Baryons Multiquarks and other exotics Outlook
Light-quark baryons
An impressive description of many data with a simple tool,
But some persisting problems,
Let us concentrate on two of them
The Roper resonance = radial excitation of N or ∆
In most models, predicted above the orbital excitations with
P = −1
Similar to ψ ′ > χJ
This is unavoidable with models with ∆V (r) > 0
One suggestion: Yukawa type of interaction among quarks
(Glozmann)
Missing states, e.g., [20, 1 + ]
Absent or not seen since weakly coupled to usual entrance
channels?
A quark-diquark model has been proposed (Lichtenberg, Torino
group)
And is often revisited (Jaffe-Wilczek, Maiani et al., etc.)
Warning: if D = (qq) taken seriously, do you predict ( ¯ DD) or
(DDD)? New spectroscopy!
JMR Quark Model