Electromagnetic Properties of S11 States in a Light Cone Quark Model

Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S₁₁ resonances, N(1535) and N(1650), and the helicity amplitudes A_1/2 and S_1/2 for electroexcitation of the S₁₁ resonances from the nucleon. The electromagnetic form factors of these S₁₁ resonances are found to be similar to those of the nucleon in shape, while the charge form factor of neutral N(1650) is nearly zero. The relative peak height of the S₁₁ charge form factors is controlled by the mixing angle common to both resonance wave functions. As in most quark models, there is a systematic overestimate of A^p_1/2 in both N(1535) and N(1650) cases at the photon point. A sizeable S_1/2 for all cases is produced as suggested by experiments.