Eta photoproduction of nucleons and the structure of the resonance S11(1535) in the quark model.

Abstract

In this paper, we present our study on the $\eta$ photoproduction based on the chiral quark model. We find that quark model provides a very good description of the $\eta$ production with much less parameters, and the threshold region is not a reliable source to determine the $\eta NN$ coupling constant due to its strong dependence on the properties of the resonance $S_{11}(1535)$. We suggest that the systematic data in $E_{lab}=1.2 \sim 1.4$ GeV region may help us to determine the $\eta NN$ coupling constant more precisely. The structure of the resonance $S_{11}(1535)$ is discussed, we find that the recent data from Mainz group bring the helicity amplitude much closer to the quark model prediction. However, more studies need to be done to understand the large $\eta N$ branching ratio of the resonance $S_{11}(1535)$. Our results show that the quark model is a very good approach to study the underlying structure of baryon resonances from the meson photoproduction data.