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动力学耦合道模型中核子共振电磁跃迁形状因子的提取

Extraction of Electromagnetic Transition Form Factors for Nucleon Resonances within a Dynamical Coupled-Channels Model

N. Suzuki, T. Sato, T. -S. H. Lee

备注：
10 pages, 12 figures
发表信息：
Phys.Rev.C82:045206,2010
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摘要：

我们解释了最近发展的解析延拓方法在提取核子共振电磁跃迁形状因子中的应用在介子-重子反应的动力学耦合通道模型中的$N^*$（$N^*$）。对于良好隔离的$P_{33}$和$D_{13}$，在复能量平面上的共振极点位置处定义的所获得的$N^*\rightarrow γN$跃迁形状因子的说明性结果，并给出了复杂的$P_{11}$共振。一个公式已经开发出一个统一的表示的影响，由于前两个$P_{11}$极点，这是附近的$πΔ$阈值，但在不同的黎曼面。我们还发现，一个简单的公式，其参数确定在劳伦展开的$πN \rightarrow πN$和$γN \rightarrowπN$振幅，可以重现在很大程度上所考虑的模型在能量附近的提取的共振位置的实部的精确解。我们指出我们的结果和那些提取的方法使用Breit-Wigner参数化的共振振幅，以适应数据之间的差异。

英文摘要：

We explain the application of a recently developed analytic continuation method to extract the electromagnetic transition form factors for the nucleon resonances ($N^*$) within a dynamical coupled-channel model of meson-baryon reactions.Illustrative results of the obtained $N^*\rightarrow γN$ transition form factors, defined at the resonance pole positions on the complex energy plane, for the well isolated $P_{33}$ and $D_{13}$, and the complicated $P_{11}$ resonances are presented. A formula has been developed to give an unified representation of the effects due to the first two $P_{11}$ poles, which are near the $πΔ$ threshold, but are on different Riemann sheets. We also find that a simple formula, with its parameters determined in the Laurent expansions of $πN \rightarrow πN$ and $γN \rightarrowπN$ amplitudes, can reproduce to a very large extent the exact solutions of the considered model at energies near the real parts of the extracted resonance positions. We indicate the differences between our results and those extracted from the approaches using the Breit-Wigner parametrization of resonant amplitudes to fit the data.

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