分波分析中复杂分支点的相关性
Relevance of complex branch points for partial wave analysis
摘要：
强子谱学的一个中心问题是从实验数据中推导和解释共振参数，即极位和留数，因为这些是与格点量子色动力学或模型计算相比较的量。然而，并非所有可观测量的结构都来自共振极点：原点也可能是分支点，要么位于实轴上（当一个新的通道由稳定粒子组成时），要么位于复平面上（当至少有一个中间粒子不稳定时）。在本文中，我们首先证明存在这样的分支点在复杂的平面上，然后显示的例子中的π N P11分波，它是不可能区分的结构引起的后者从一个真正的极点信号的基础上的弹性数据。
英文摘要：
A central issue in hadron spectroscopy is to deduce --- and interpret --- resonance parameters, namely pole positions and residues, from experimental data, for those are the quantities to be compared to lattice QCD or model calculations. However, not every structure in the observables derives from a resonance pole: the origin might as well be branch points, either located on the real axis (when a new channel comprised of stable particles opens) or in the complex plane (when at least one of the intermediate particles is unstable). In this paper we demonstrate first the existence of such branch points in the complex plane and then show on the example of the piN P11 partial wave that it is not possible to distinguish the structures induced by the latter from a true pole signal based on elastic data alone.
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