We refine our previous calculation of multipole amplitude 𝐸0+ for pion photoproduction process, 𝛾⁢𝑁→𝜋⁢𝑁. The treatment of final-state interactions is based upon an earlier analysis of pion-nucleon scattering within Hamiltonian effective field theory, supplemented by incorporating contributions from the 𝑁*⁡(1650) and the 𝐾⁢Λ coupled channel. The contribution from the bare state corresponding to the 𝑁*⁡(1650) significantly enhances our results. Additionally, we also compute the multipole amplitude 𝑀1−, which is of direct relevance to the Roper resonance. The results are comparable with other dynamical coupled-channel models, even though the contribution from the bare state (interpreted as a 2⁢𝑠 excitation) in this channel is small because of its large mass.

中文翻译：

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用哈密顿有效场论产生核子激发态的 Pion 光生产


我们改进了之前对 π 光产生过程的多极振幅 E0+ γN→πN 的计算。最终状态相互作用的处理基于哈密顿有效场论中对 π 子-核子散射的早期分析，并结合 N*（1650） 和 KΛ 耦合通道的贡献进行补充。对应于 N*（1650） 的裸状态的贡献显着增强了我们的结果。此外，我们还计算了多极振幅 M1−，它与 Roper 谐振直接相关。结果与其他动态耦合通道模型相当，尽管由于质量大，裸状态（解释为 2s 激励）在该通道中的贡献很小。