Current Algebra and Photoproduction of Pions

TLDR: In this paper, a low-energy theorem from current-algebra techniques is employed to derive an expression for the pion photoproduction amplitude which is shown to be gauge invariant.

Abstract: A low-energy theorem from current-algebra techniques is employed to derive an expression for the pion photoproduction amplitude which is shown to be gauge invariant. The low-energy predictions for the differential cross sections and the multipole amplitudes are analyzed extensively and compared with the experimental data. The predictions for the production of charged pions are in as good agreement with experimental data as those of dispersion theory are. However, the current-algebra predictions for $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}p$ characteristically differ from other theoretical models, especially at threshold. Accurate low-energy experimental data for this process should therefore provide a test of the validity of the current-algebra approach.