Electromagnetic form factor of nucleon resonances from meson production

The nucleon resonances appear as poles of the scattering amplitudes on the complex energy plane. The masses of $N^*$ and the electromagnetic $NN^*$ transition form factors are obtained from the pole positions and the residues of the scattering amplitudes. We have developed a method of analytic continuation to extract resonance parameters from the amplitudes of the dynamical reaction model, which includes unstable particle channels such as $\pi\Delta, \sigma N$ and $\rho N$. We apply the method for the $\pi N$ and $\gamma^* N$ amplitudes from our coupled channel model of meson production reactions. The extracted $NN^*$ form factors for a few $N^*$ resonances will be presented.