The E1+/M1+ and S1+/M1+ratios of gamma N ->Delta(1232) with a point-form relativistic quantum mechanics

The point-form relativistic quantum mechanics is employed to study the photo- and electro-productions of the nucleon resonances. Both the ratios of E1+/M1+ and S1+/M1+ of gamma N -> Delta transition are calculated. Configuration mixing effect is simply included. The results of the point-form relativistic quantum mechanics indicate that the relativistic effects provide a remarkable role both on the transition amplitudes and on the two ratios E1+/M1+ and S1+/M1+. It is found that small deformations of the nucleon and A resonance wave functions in D-wave can provides more sizable ratios in the point-form relativistic quantum mechanics than in the conventional non-relativistic constituent quark model. (c) 2006 Elsevier B.V. All rights reserved.