Within a chiral constituent quark model approach, $\eta$-meson production on the proton { \it via} electromagnetic and hadron probes are studied. With few parameters, differential cross-section and polarized beam asymmetry for \gamma p \to \eta p$ and differential cross section for $\pi^- p\to \eta n$ processes are calculated and successfully compared with the data in the center-of-mass energy range from threshold up to 2 GeV. The five known resonances $S_{ 11}(1535)$, $S_{ 11}(1650)$, $P_{ 13}(1720)$, $D_{ 13}(1520)$, and $F_{ 15}(1680)$ are found to be dominant in the reaction mechanisms in both channels. Possible roles plaied by new resonances are also investigated and in the photoproduction channel, significant contribution from $S_{ 11}$- and $D_{ 15}$-resonances, with masses around 1715 MeV and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of $N^* \to \pi N, \eta N$ are also presented, and found consistent with the PDG values.
Categories: nucl-th