Study of nucleon resonances in a chiral quark model via η productions

In this report we investigate η-meson productions on the proton via electromagnetic and hadron probes in a chiral quark model approach. The observables, such as, differential cross section and beam asymmetry for the two productions are calculated and compared with the experiment. The five known resonances S11(1535), S11(1650), P13(1720), D13(1520), and F15(1680) are found to be dominant in the reaction mechanisms in both channels. Significant contribution from a new S11 resonances are deduced. For the so-called 'missing resonances', no evidence is found within the investigated reactions. The partial wave amplitudes for π-p → ηn are also presented. (authors)