Pion photoproduction on nucleons from threshold tO Eγ = 230 MeV

Abstract

Single-pion photoproduction at low energy is investigated on the basis of the current algebra phenomenological lagrangian modified to provide an agreement of multipole amplitudes of the γp → π 0p reaction at the threshold with experiments. There are five free parameters (coupling constants) which the amplitudes of pion photoproduction processes depend on. Only one of them survives after we assume that the unmodified model gives a reasonably good description of π + photoproduction. It has been found from the threshold value of the E 0+ suπ 0 multipole. It appears that the single successful interpretation of the neutral pion photoproduction reaction is impossible throughout the photon energy region from threshold to 230 MeV. More data are needed on π° photoproduction for backward and (especially) forward directions to decide definitely whether current algebra predictions of pion photoproduction can be compatible with experimental data.