Experimental data for pion photoproduction including differential cross sections and various polarization observables from four reaction channels, $\gamma p\to {\pi }^{0}p, \gamma p\to {\pi }^{+}n, \gamma n\to {\pi }^{-}p$, and $\gamma n\to {\pi }^{0}n$, 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 $W\approx 1.6$ GeV in many partial waves. Electromagnetic multipoles $E_{\ell \pm }$ and $M_{\ell \pm }$ are presented and discussed for $S,P,D$, and $F$ waves.

中文翻译：

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具有固定解析度的 pion 光生产的单能分波分析

pion 光产生的实验数据，包括来自四个反应通道的不同截面和各种偏振可观测值， $\gamma 磷\to {\pi }^0磷, \gamma 磷\to {\pi }^{+}n, \gamma n\to {\pi }^{-}磷$， 和 $\gamma n\to {\pi }^{0}n$，从阈值到 $宽=2.2$ GeV 用于通过施加单一性和固定-$吨$迭代过程中的分析性。反应模型仅用作第一次迭代的起点。我们证明了通过这个程序可以获得部分波振幅，它只显示对初始模型假设的最小依赖。分析是在完全同位旋中获得的，沃森定理适用于以下能量$宽=1.3$ GeV 但甚至达到 $宽\approx 1.6$GeV 在许多部分波中。电磁多极${乙}_{\ell \pm }$ 和 ${米}_{\ell \pm }$ 被提出和讨论 $秒,磷,D$， 和 $F$ 波浪。