| 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 $\\pi^- p\\rightarrow \\eta n$ 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. |
