Quark Model Explanation of the $N^*\to Nη$ Branching Ratios

The constituent quark model can explain the strong selectivity of the $N\eta$ decay branching ratios of the nucleon resonances if the fine structure interaction between the constituent quarks is described in terms of Goldstone boson exchange. This chiral quark model predicts that the resonances $N(1535)$, $N(1710)$, $\Lambda(1670)$, $\Sigma(1750)$, which have mixed flavor and spin symmetry $[21]_{FS} [21]_F [21]_S$ wavefunctions in lowest order, should have large $N\eta$ branching ratios, while $N\eta$ decay of the other resonances that have different flavor-spin symmetry should be strongly suppressed in agreement with the experimental branching ratios.