A relativistic study of the nucleon helicity amplitudes

We perform a calculation of the relativistic transition form factors for the electromagnetic excitation of the nucleon resonances. We use as input the 3-quark wave functions obtained in a constituent quark model with three-body forces in the hypercentral approach. With respect to the non relativistic calculations a significant contribution is obtained up to Q2≅2 (GeV/c)2. However, the low Q2-behaviour exhibits a lack of strength, which may be connected with the need of taking into account explicitly further degrees of freedom beyond the three constituent quark ones. (orig.)