论文标题
$ n/d $研究$πn$散射幅度的奇异性结构
The $N/D$ study on the singularity structure of $πN$ scattering amplitudes
论文作者
论文摘要
$ n/d $方法用于研究$ s_ {11} $通道低能$πn$散射幅度。左切割的输入来自各种现象学模型。借助生产表示，可以将总相移分解为不同的贡献，它进一步揭示了亚阈值共振的存在$ n^*（890）$不取决于动态输入的细节。此外，发现存在部分波的虚拟状态，这些状态是由$ u $通道核子交换引起的。这些虚拟状态在$ u $通道段削减的终点积累。终点是因此，在复杂$ S $平面的第二张纸上全幅度的基本奇异性。
The $N/D$ method is used to study the $S_{11}$ channel low energy $πN$ scattering amplitude. The input of left cuts are obtained from various phenomenological models. With the aid of the production representation, the total phase shifts can be decomposed into different contributions, and it further reveals that the existence of subthreshold resonance $N^*(890)$ doesn't depend on the details of the dynamical input. Additionally, it is found that there exist virtual states in partial waves, which are induced by the $u$ channel nucleon exchanges. These virtual states accumulate at the end point of the $u$ channel segment cut. The end point is hence the essential singularity of the full amplitude on the second sheet of complex $s$ plane.
