ElectromagneticN→N*(1535)transition in the relativistic constituent-quark model

We study a light-cone model of the nucleon and the $S_{11}\mathrm{}\left(1535\right)\mathrm{}$ resonance which provides a relativistic generalization of the constituent-quark model in the nonperturbative low-$Q^2$ regime. The two parameters of the model, namely, the size parameter $\alpha$ and the constituent-quark mass $m_q\approx 300$ MeV, are fixed by the axial form factor. We find good agreement for the electromagnetic form factors of the nucleon up to $Q^2\approx 1-2$ Ge${\mathrm{V}}^2$. All static properties of the nucleon, except for the neutron charge radius, are reproduced within 10%. In addition, we show that the electromagnetic current of the nucleon is conserved. The $S_{11}\mathrm{}\left(1535\right)\mathrm{}$ transition amplitudes, where gauge invariance is achieved by including a three-body current, are calculated from a constraint-free form-factor set. They are in reasonable agreement with the available photo- and electroproduction data.