Chiral Dynamics for High-Spin Baryons and an Application to Double-Pion Photoproduction

Abstract

An $\mathrm{SU}(2)\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(2)$ chiral-dynamical Lagrangian for baryons of arbitrary spin and isospin is discussed. Cross sections for low-energy double-pion photoproduction from a nucleon are calculated by assuming that the nucleon and one final pion form an isobar $\ensuremath{\Delta}(1236 \mathrm{MeV})$. The results are compared with those obtained by the soft-pion dispersion-relation approach. It is shown that the static-nucleon model gives satisfactory total cross sections but is inadequate for angular-distribution differential cross sections. Our theoretical predictions are consistent with experiment.