Low-Energy Photoproduction and the Chiral-Transformation Property of the Electromagnetic Current

Abstract

Using new multipole analyses of low-energy pion photoproduction, we have examined the possibility that the electromagnetic current does not commute with the axial charge $F_3^5$. Within errors, which are not as small as one would like, there is no evidence for a lack of commutation. It is pointed out that the photoproduction amplitude which directly measures this commutator receives very little contribution from the large, well-determined $M_{1+}$ multipole and is dominated by the more exotic multipoles like $E_{1+}$.