For several decades, the \(\sigma /f_0(500)\) and \(\kappa /K_0^*(700)\) resonances have been subject to long-standing debate. Both their existence and properties were controversial until very recently. In this tutorial review, we compare model-independent dispersive and analytic techniques versus unitarized Chiral Perturbation Theory, when applied to the lightest scalar mesons \(\sigma /f_0(500) \) and \(\kappa /K_0^*(700) \). Generically, the former have settled the long-standing controversy about the existence of these states, providing a precise determination of their parameters, whereas unitarization of chiral effective theories allows us to understand their nature, spectroscopic classification and dependence on QCD parameters. Here we review in a pedagogical way their uses, advantages and caveats.

几十年来，\(\sigma /f_0(500)\)和\(\kappa /K_0^*(700)\)共振一直受到长期争论的影响。直到最近，它们的存在和属性都存在争议。在本教程回顾中，当应用于最轻的标量介子\(\sigma /f_0(500) \)和\(\kappa /K_0^*(700) \). 一般来说，前者解决了关于这些状态存在的长期争议，提供了它们参数的精确确定，而手性有效理论的单一化使我们能够了解它们的性质、光谱分类和对 QCD 参数的依赖性。在这里，我们以教学的方式回顾了它们的用途、优点和注意事项。