He, J (reprint author), Chinese Acad Sci, Inst High Energy Phys, POB 918-4, Beijing 100049, Peoples R China.
Using relativistic spin-flavor wave functions of a L'orentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S-11 resonances, N(1535) and N(1650), and the helicity amplitudes A(1/2), and S-1/2 for electroexcitation of the S-11 resonances from the nucleon. The electromagnetic form factors of these S-11 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 S-11 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(1/2)p 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.