Multipole amplitudes of pion photoproduction on nucleons up to 2GeV using dispersion relations and the unitary isobar model

Two approaches for the analysis of pion photoproduction and electroproduction on nucleons in the resonance energy region are checked at Q²=0 using the results of the GWU(VPI) partial-wave analysis of photoproduction data. The approaches are based on dispersion relations and the unitary isobar model. Within dispersion relations a good description of photoproduction multipoles is obtained up to W=1.8GeV. Within the unitary isobar model, modified with increasing energy by the incorporation of Regge poles and with a unified Breit-Wigner parametrization of resonance contributions, a good description of photoproduction multipoles is obtained up to W=2GeV.