Implications of baryon magnetic moments for the quark model

The implications of recent baryon-magnetic-moment measurements for various assumptions in the quark model are considered. The static quark model is seen to give a qualitative understanding of the baryon magnetic moments, but fails in a quantitative test ($\frac{{\chi }^2}{\mathrm{DF}}=\frac{21.5}{5}$), largely due to inconsistency of the now accurate determinations of the ${\Lambda }^0$ and ${\Xi }^0$ moments. Introducing nonstatic effects (orbital, relativistic, or exchange) still permits four independent sum rules to be written (for eight moments) if approximate SU(3) symmetry is assumed for quark-model wave functions. Two sum rules give good agreement with experiment, but those sum rules for any case involving the ${\Xi }^{-}$ or ${\Sigma }^{-}$ moments do not, suggesting that their experimental determination is inconsistent with such a quark model.