Quark-Model Comparison on the Narrowe+e−Resonances

The narrow $e^{+}{e}^{-}$ resonances $\psi (3.1\mathrm{} \mathrm{GeV}/c^2)$ and $\psi (3.7\mathrm{} \mathrm{GeV}/c^2)$ are used to test quark models: SU(3) ⊗ SU(3)′ encompasses them readily but also predicts four more such states; SU(4) includes more than one state only by extension to ($q\overline{q} q\overline{q}$) representations; the two-triplet model encounters severe difficulties; and scalar colored quarks seem practically excluded. The importance of photoproduction, especially of charged counterparts, is emphasized.