Received 15 July 2021
Accepted 20 August 2021
DOI:https://doi.org/10.1103/PhysRevC.104.034605
©2021 American Physical Society
Abstract
Experimental data for pion photoproduction including differential cross sections and various polarization observables from four reaction channels, $\gamma p \rightarrow \pi^0 p$, $\gamma p \rightarrow \pi^+ n$, $\gamma n \rightarrow \pi^− p$, and $\gamma n \rightarrow \pi^0 n$, 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≈ 1.6 GeV in many partial waves. Electromagnetic multipoles $E_{ℓ\pm}$ and $M _{ℓ\pm}$ are presented and discussed for S, P, D, and F waves.
