Poles and Resonances inηProduction

Poles and resonances are used to find ${\chi }^2$ fits to the data up to several hundred MeV above threshold for the processes ${\pi }^{-}+p\to n+\eta$ and $\gamma +p\to p+\eta$. Below center-of-mass energy $W=1700\mathrm{}$ MeV, a consistent picture of these reactions is achieved with the following ingredients: a nucleon pole and $P_{11}\mathrm{}\left(1400\right)\mathrm{}$, $S_{11}\mathrm{}\left(1570\right)\mathrm{}$, and $D_{13}\mathrm{}\left(1512\right)\mathrm{}$ resonances for production by pions; a nucleon pole, a vector meson pole, and $S_{11}\mathrm{}\left(1570\right)\mathrm{}$ and $D_{13}\mathrm{}\left(1512\right)\mathrm{}$ resonances for photoproduction. Some $F_{15}\mathrm{}\left(1688\right)\mathrm{}$ also improves the fits. The value of the $\eta$-nucleon coupling constant, $\frac{{g_{\eta }}^2}{4\pi }$ is $\lesssim 0.002$ in both processes. Implications of these results for quark models and $\mathrm{SU}\left(3\right)\mathrm{}$ symmetry are discussed. Above $W=1700\mathrm{}$, possible additional resonances are considered in $\eta$ production by pions.