Helicity and isospin asymmetries in the electroproduction of nucleon resonances

We investigate the helicity asymmetries and isospin ratios of radiative transition amplitudes for nucleon resonances electroproduced off proton and neutron targets at momentum transfers of Q2≤3 GeV2. Calculations were done in the framework of a relativized constituent quark model which includes many-body effects due to the quark interaction potential and a consistent relativistic approximation of the center-of-mass motion of the three-quark system. We find significant deviations from the predictions of the nonrelativistic quark models and the SU(6)W algebraic approach based on the single-quark-transition hypothesis. Our calculated relativistic corrections lead to an overall better agreement with the experimental data. The question of whether some of the low-lying P-wave baryons are of hybrid nature is briefly discussed. Finally we analyze the electroexcitation of the missing (20,1+) P-wave resonances