标题： 共振的极点性质：何时减去部分衰变宽度以获得极点宽度 显示英文标题

标题： Pole properties of a resonance: When to subtract partial-decay widths to obtain the pole widths

摘要： 当一个共振态靠近较重通道的阈值时，可能会出现一个有趣的特性。 这里采用的典型例子是标量同位旋为0的$f_0(980)$共振态，它与较轻的$\pi\pi$和较重的$K\bar{K}$通道耦合。 结果表明，衰变宽度由部分衰变宽度的和或差给出，这取决于极点位于与物理页相邻的黎曼面之上或之下，分别对应于$K\bar{K}$阈值之上或之下。 接下来，我们表明，在 Flatté 或能量依赖的 Breit-Wigner 参数化中通常被忽略的裸参数重整化对于提取物理信息至关重要。 通过使用与 Roy 方程和其他解析约束得到的极点性质相匹配的 Flatté 参数化，评估了$f_0(980)$的复合性。 显示英文摘要

摘要： When a resonance lies near the threshold of a heavier channel, an interesting feature can occur. The paradigmatic example employed here is the scalar isoscalar $f_0(980)$ resonance that couples to the lighter $\pi\pi$ and heavier $K\bar{K}$ channels. It is shown that the decay width is given by the sum or subtraction of the partial decay widths depending on whether the pole lies in the Riemann sheet that is contiguous with the physical one above or below the $K\bar{K}$ threshold, respectively. Next, we show that the usually disregarded renormalization of bare parameters in Flatt\'e or energy-dependent Breit-Wigner parameterizations is essential to extract physical information. The compositeness of the $f_0(980)$ by using a Flatt\'e parameterization matched to reproduce the pole properties obtained from Roy equations and other analytic constraints is evaluated.