Semitauonic b -hadron decays: A lepton flavor universality laboratory
Semitauonic b -hadron decays: A lepton flavor universality laboratory
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DOI：
10.1103/revmodphys.94.015003
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发表时间：
2021-01
影响因子：
44.1
通讯作者：
F. Bernlochner;M. Franco Sevilla;D. Robinson;G. Wormser
中科院分区：
文献类型：
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作者：
F. Bernlochner;M. Franco Sevilla;D. Robinson;G. Wormser
鉴于测量的分支分数长期存在异常，以及 LHC 和 Belle II 预期的非常大的数据集，半重 $b$-强子衰变中轻子味道普遍性破坏 (LFUV) 的研究变得越来越重要。在这篇综述中，我们对 $B$ 工厂和大型强子对撞机的半轻子 LFUV 测量的实验环境和方法进行了全面的调查，并对各种半轻子衰变可观测值的理论基础和预测进行了简要概述。我们继续研究未来的前景，将系统不确定性控制在百分比水平，与标准模型（SM）预测的精度相匹配。此外，我们讨论了 LFUV 数据组合的新观点和注意事项，并重新审视了 ${\cal R}(D^{(*)})$ 比率的世界平均值。在这里，我们证明对 $D^{**}$ 激发态不确定性相关性的不同处理可以在 $1\sigma$ 范围内改变当前 $3\sigma$ 与 SM 的张力。之前对 $D^{**}\tau\nu$ 贡献的实验高估可能会进一步加剧这种情况。还估计了未来测量的精度；简要探讨了它们利用全差分信息的能力，以及解决 LFUV 可观测量的自洽新物理解释中固有困难的解决方案。
The study of lepton flavor universality violation (LFUV) in semitauonic $b$-hadron decays has become increasingly important in light of longstanding anomalies in their measured branching fractions, and the very large datasets anticipated from the LHC and Belle II. In this review, we undertake a comprehensive survey of the experimental environments and methodologies for semitauonic LFUV measurements at the $B$-factories and LHCb, along with a concise overview of the theoretical foundations and predictions for a wide range of semileptonic decay observables. We proceed to examine the future prospects to control systematic uncertainties down to the percent level, matching the precision of Standard Model (SM) predictions. Furthermore, we discuss new perspectives and caveats on combinations of the LFUV data and revisit the world averages for the ${\cal R}(D^{(*)})$ ratios. Here we demonstrate that different treatments for the correlations of uncertainties from $D^{**}$ excited states can vary the current $3\sigma$ tension with the SM within a $1\sigma$ range. Prior experimental overestimates of $D^{**}\tau\nu$ contributions may further exacerbate this. The precision of future measurements is also estimated; their power to exploit full differential information, and solutions to the inherent difficulties in self-consistent new physics interpretations of LFUV observables, are briefly explored.