Single-Energy Partial-Wave Analysis For Pion Photoproduction With Fixed-T Analyticity

Experimental data for pion photoproduction including differential cross sections and various polarization observables from four reaction channels, gamma p -> pi(0)p, gamma p -> pi(+)n, gamma n -> pi(-) p, and gamma n -> pi(0)n, from threshold up to W = 2.2 GeV were used in order to perform a single-energy partial-wave analysis with minimal model dependence by imposing constraints from unitarity and fixed-t analyticity in an iterative procedure. Reaction models were only used as a starting point in the very first iteration. We demonstrate that with this procedure partial-wave amplitudes can be obtained which show only a minimal dependence on the initial model assumptions. The analysis was obtained in full isospin, and the Watson theorem is enforced for energies below W = 1.3 GeV but is even fulfilled up to W approximate to 1.6 GeV in many partial waves. Electromagnetic multipoles E-l +/- and M-l +/- are presented and discussed for S, P, D, and F waves.