D-state configurations in the electromagnetic form factors of the nucleon and the Delta(1232) resonance

摘要

The Delta-N electromagnetic transition form factors are calculated in a schematic Poincare covariant quark model in three forms of relativistic kinematics. Addition of D-state components to pure S-state model wave functions, chosen so as to reproduce the empirical elastic electromagnetic nucleon form factors with single constituent currents, brings the calculated R-EM ratio for the Delta(1232) -> N gamma transition closer to the empirical values in instant and point form kinematics. The calculated R-SM ratio is insensitive to the D-state component. In front form kinematics the substantial violation of the angular condition for the spin 3/2 resonance transition amplitude in the impulse approximation prevents a unique determination of R-EM and R-SM, both of which are very sensitive to D-state components. In no form of kinematics do D-state deformations of the rest frame baryon wave functions alone suffice for a description of the empirical values of these ratios. (c) 2005 Elsevier B.V. All rights reserved.