Multipole amplitudes of pion photoproduction on nucleons up to 2 GeV 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 Q(2)=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=1.8 GeV. 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=2 GeV.