Delta(1232) electroproduction amplitudes in chiral soliton models of the nucleon - art. no. 045202

The multipole amplitudes for the N-Delta(1232) electromagnetic transition a re computed in the framework of the linear a model and the chiral chromodie lectric model for small and moderate photon virtualities. The models includ e quark and meson degrees of freedom and the nucleon and the Delta are clus ters of three valence hedgehog quarks surrounded by meson clouds described by coherent states. Angular momentum and isospin projections are performed to endow model states representing the nucleon and the a with proper quantu m numbers. Recoil corrections involved in the process gamma(v)N-->Delta are taken into account by performing linear momentum projection of the initial and final baryon states. The ratios E2/M1 and C2/M1 are in good agreement with the data in the two models, but the magnetic amplitude is better repro duced in the linear sigma model. The ratios show little dependence with the model parameters. Both in the linear sigma model and in the chromodielectr ic model the charged pions are responsible for the nonvanishing quadrupole- electric and -Coulomb amplitudes. The recoil corrections enhance the result s obtained for the amplitudes without linear momentum projection, improving the comparison with experimental data. The dependence of the theoretical a mplitudes with the choice of the reference frame is also studied.