Pion photoproduction in theΔ(1232)region and chiral bag models

We calculate pion photoproduction near the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance using a version of the chiral bag model based on an effective Lagrangian that reproduces correct pion-nucleon phenomenology through third order in the pion field. The pionic corrections to the $M1\mathrm{}$ (or $M1+$) amplitude are common to a broad class of chiral bag models and substantially improve agreement with experiment. We treat also the $E2\mathrm{}$ (or $E1+$) multipole which is accessible in our approach since the effective Lagrangian induces quark-quark tensor coupling through pion exchange; this in turn permits the admixture of baryon components involving quark excitation to $d$ states. The resulting $E2\mathrm{}$ admixture is consistent with the rather loose bounds set by the present experimental information on this quantity. The present work neglects the tensor force and $d$ state arising from gluon exchange between quarks.