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

Abstract

The $\Delta -N$ electromagnetic transition form factors are calculated in the Poincaré 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 $\Delta (1232)\to N\gamma$ 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.

Comments: 11 figures, elsevier format