论文标题
两体过渡振幅的壳上表示：单个外部电流
On-shell representations of two-body transition amplitudes: single external current
论文作者
论文摘要
这项工作探讨了通过单个外部电流插入二两个粒子系统的散射振幅，$ 2+\ Mathcal {J} \至2 $。这样的幅度可以提供有关激发QCD光谱的结构信息。我们得出了这些反应的精确分析表示。从这些振幅中，我们显示了如何严格定义共振和绑定状态形式因子。此外，我们探讨了幅度狭窄宽度极限的后果以及沃德 - 塔卡哈西（Ward-Takahashi）身份对保守向量电流的作用。这些结果适用于任何数量的两体通道，没有固有的自旋，并且具有任意Lorentz结构和量子数的电流。这项工作和现有的有限体积形式主义提供了一个完整的框架，用于确定Lattice QCD的这类幅度。
This work explores scattering amplitudes that couple two-particle systems via a single external current insertion, $2+\mathcal{J}\to 2$. Such amplitudes can provide structural information about the excited QCD spectrum. We derive an exact analytic representation for these reactions. From these amplitudes, we show how to rigorously define resonance and bound-state form-factors. Furthermore, we explore the consequences of the narrow-width limit of the amplitudes as well as the role of the Ward-Takahashi identity for conserved vector currents. These results hold for any number of two-body channels with no intrinsic spin, and a current with arbitrary Lorentz structure and quantum numbers. This work and the existing finite-volume formalism provide a complete framework for determining this class of amplitudes from lattice QCD.
