胶球：没有夸克的强子
Glueballs: hadrons without quarks
- Université de Mons, UMONS Research Institute for Complex Systems（蒙斯大学，复杂系统研究所）
- Universitat de Barcelona（巴塞罗那大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文综述胶球（纯胶子束缚态）的理论与实验研究，涵盖量子数、谱、混合与衰变，评估候选态并展望未来验证计划。
AI中文摘要：
胶球是由纯胶子构成的色单态束缚态。它们是量子色动力学（QCD）非阿贝尔结构的不可避免的结果，并且在纯杨-米尔斯极限下，它们是该理论唯一的物理激发态。本文回顾了关于胶球已知的知识。在确定两胶子和三胶子态可以携带的自旋、宇称和电荷共轭量子数之后，综述了纯规范谱。简要介绍了每种主要的理论方法及其各自的结论，包括格点QCD、组分胶子和库仑规范模型、泛函Dyson-Schwinger和Bethe-Salpeter方程、全息模型以及QCD求和规则。特别关注了标度设定模糊性，该模糊性限制了淬火胶球质量转换为物理单位的精度。随后讨论转向完整QCD。在讨论胶球指定在此语境中的含义之后，解决了非淬火效应以及与胶球-$q\bar{q}$混合相关的问题。介绍了支撑混合图像的大$N_c$计数，以及混合的质量矩阵和有效拉格朗日处理。还讨论了塑造胶球衰变的选择规则和动力学机制。最后回顾了实验中使用的富含胶子的产生机制。逐扇区评估候选者：$f_0(1370)/f_0(1500)/f_0(1710)$以及标量扇区的竞争性解释，赝标量扇区的$\eta(1405)/\eta(1475)$和$X(2370)$，拥挤的张量区域，以及基本上未探索的$C=-1$扇区及其与Odderon的联系。作为结论，回顾了可能有助于验证其中一些候选者或识别其他候选者的计划的前景。
英文摘要：
Glueballs are colour-singlet bound states built from gluons alone. They are an unavoidable consequence of the non-Abelian structure of Quantum Chromodynamics (QCD), and, in the pure Yang--Mills limit, they are the only physical excitations of the theory. The present article reviews what is known about them. After establishing which spin, parity and charge-conjugation quantum numbers two- and three-gluon states can carry, the pure-gauge spectrum is surveyed. Each of the main theoretical approaches and their respective conclusions are briefly presented. They include lattice QCD, constituent-gluon and Coulomb-gauge models, functional Dyson--Schwinger and Bethe--Salpeter equations, holographic models, and QCD sum rules. Particular attention is paid to the scale-setting ambiguity that limits how precisely a quenched glueball mass can be converted into physical units. The discussion then turns to full QCD. After discussing the meaning of a glueball assignment in this context, unquenching effects and questions related to glueball--$q\bar{q}$ mixing are addressed. The large-$N_c$ counting that underpins the mixing picture, as well as mass-matrix and effective-Lagrangian treatments of mixing are presented. The selection rules and dynamical mechanisms that shape glueball decays are also discussed. The gluon-rich production mechanisms used experimentally are finally reviewed. The candidates are assessed sector by sector: $f_0(1370)/f_0(1500)/f_0(1710)$ and the competing interpretations of the scalar sector, $η(1405)/η(1475)$ and $X(2370)$ in the pseudoscalar sector, the crowded tensor region, and the essentially unexplored $C=-1$ sector and its connection to the Odderon. Outlooks on the programmes that could help in validating some of these candidates or identifying others are reviewed as a conclusion.
