Abstract Undeniably, the naturalness principle has had a major role in particle physics during the last decades, in particular in model building. Nowadays, one can find a wide range of different definitions. Some of them seem mutually exclusive, but traditionally, its notion has been linked to the fine-tuning problem. Understanding naturalness as the imposition that fine-tuning problems have to vanish, for instance, due to the existence of new particles, new models as those based in supersymmetry were built. In order to palliate the fine-tuning problem the Higgs sector of the standard model seems to suffer, new physics should have appeared already in the last LHC run. Thus, the persistence of fine-tuning has originated numerous works exploring both, the limits and the different conceptual definitions of naturalness. However, little work has been done re-examining precisely one of the main pillars naturalness advocates: its historical successes. Given the current period in which the critics to the naturalness principle are undergoing, we find important to explore in detail the historical examples often cited, primarily the charm quark proposal and its mass prediction, and see how can this contribute to the debate.

中文翻译：

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夸克自然成功

摘要不可否认，在过去的几十年中，自然原理在粒子物理学中发挥了重要作用，尤其是在模型构建中。如今，人们可以找到各种各样的不同定义。它们中的一些似乎互斥，但传统上，其概念已与微调问题联系在一起。将自然理解为微调问题必须消失的表现，例如，由于存在新粒子，建立了基于超对称性的新模型。为了缓解微调问题，标准模型的希格斯部门似乎遭受了打击，新的物理学应该在上一次大型强子对撞机运行中已经出现。因此，微调的持久性源于许多探索自然界的极限和不同概念定义的作品。然而，很少进行任何工作来重新审视自然性倡导者的主要支柱之一：其历史成就。考虑到当前对自然性原理的批评者正在经历的时期，我们发现重要的是，详细探讨经常被引用的历史实例，主要是魅力夸克的提议及其大规模预测，并观察这如何有助于辩论。