Two topics have recently risen to prominence within the ongoing searches of beyond–Standard Model effects in b and c decays: observables that test lepton flavor universality (LFU) and those that test lepton flavor violation (LFV). A coherent set of measurements suggests nonstandard LFU effects. General arguments relate LFU to LFV, and the observed size of the former gives hope of observable signals for the latter. We attempt a comprehensive discussion of both theoretical and experimental aspects of these tests. The main final message is that all the instruments necessary to fully establish the putative new effects are at hand, thanks to running experiments and their upgrades. Therefore, this subject stands a concrete chance of ushering in genuinely unexpected discoveries.

中文翻译：

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b 和 c 衰变中的轻子味违规和轻子味普遍性违规


最近，在 b 和 c 衰变中超标准模型效应的持续研究中，两个主题变得突出：测试轻子风味普遍性 (LFU) 的可观测量和测试轻子风味破坏 (LFV) 的可观测量。一组连贯的测量表明非标准的 LFU 效应。一般论点将 LFU 与 LFV 联系起来，观察到的前者的大小为后者提供了可观察到的信号的希望。我们尝试对这些测试的理论和实验方面进行全面讨论。最后的主要信息是，通过运行实验及其升级，完全建立假定的新效果所需的所有工具都已准备就绪。因此，这个主题有可能带来真正意想不到的发现。