标题： 轻介子的手征微扰理论的状态 显示英文标题

标题： Status of chiral perturbation theory for light mesons

摘要： 手征微扰理论在介子区的现状通过几个热门例子进行了说明。 带电π介子极化率的理论与实验长期存在差异，现在已经解决，结果支持到下一阶的下一阶的SU(2)手征结果。 对于手征SU(3)，主要障碍是大量未知的耦合常数（LECs）以及在许多感兴趣的情况下低能展开缺乏收敛性。 我描述了一种对强作用区LECs的新全局拟合，该拟合导致对CKM矩阵元$V_{us}$的预测，与最新的格点计算结果一致。 手征级数的缓慢收敛在具有强末态相互作用的转变中尤为明显，需要采用色散处理方法。 对色散方法在$K_{\ell 4}$衰变和$\eta -> 3 \pi$衰变中的应用现状进行了综述，在这些衰变中，最近已经获得了Dalitz图分布的精确测量。 显示英文摘要

摘要： The status of chiral perturbation theory in the meson sector is illustrated with several topical examples. The longtime discrepancy between theory and experiment for the charged pion polarizabilities has now been resolved in favour of the chiral SU(2) result to next-to-next-to-leading order. For chiral SU(3), the main obstacles are the large number of badly known coupling constants (LECs) and the lack of convergence of the low-energy expansion in many cases of interest. I describe a new global fit of the LECs in the strong sector that leads to a prediction of the CKM matrix element $V_{us}$ in agreement with the latest lattice determinations. The slow convergence of the chiral series is particularly acute in transitions with strong final-state interactions calling for dispersive treatments. The status of dispersive approaches is reviewed for $K_{\ell 4}$ decays and for $\eta -> 3 \pi$ decays where precise measurements of Dalitz plot distributions have recently become available.