arXiv 1801.011122018-01hep-phhep-ex

在$b\to c\ellν$跃迁中约束新物理

Constraining new physics in $b\to c\ellν$ transitions

Martin Jung, David M. Straub

备注：: 27 pages, 8 figures. v3: minor clarifications, conclusions unchanged
DOI：: 10.1007/JHEP01(2019)009

摘要：

$B$衰变通过$b\to c\ellν$与$\ell=e$或$μ$的跃迁进行，是标准模型中的树级过程。它们用于测量CKM元素$V_{cb}$，因此在确定例如幺正三角形中形成重要成分;因此，新物理学贡献能在多大程度上影响它们的问题很重要，特别是考虑到$V_{cb}$决定之间的长期紧张关系，从包容性和排他性的衰变和显着的暗示轻子味普适性违反$b\to cτν$和$b\to s\ell\ell$衰变。我们执行一个全面的模型独立的分析新的物理在$b\to c\ellν$，考虑所有的标量，矢量和张量的相互作用发生在单介质的情况下的组合。为此，我们包括第一次微分分布的$B\to D^*\ellν$角度可观的。我们表明，这些是有价值的约束非标准的相互作用。具体而言，$B\to D\ellν$谱的零反冲端点对标量电流极其敏感，而具有横向极化$D^*$的$B\to D^*\ellν$谱的最大反冲端点对张量电流极其敏感。我们还量化了$b\to c\ellν$转换中$e$ - $μ$普遍性违反的空间，由一些模型预测，建议解决$b\to cτν$异常，首次从全局拟合到$B\to D\ellν$和$B\to D^*\ellν$。具体的新的物理模型，对应于所有可能的树级介质，也进行了讨论。作为一个副作用，我们提出了$V_{cb}$确定从排他性的$B$衰变，无论是与频率和贝叶斯统计，导致兼容的结果。整个数值分析基于开源代码，一旦有新数据或新的外形尺寸可用，就可以轻松进行调整。

英文摘要：

$B$ decays proceeding via $b\to c\ellν$ transitions with $\ell=e$ or $μ$ are tree-level processes in the Standard Model. They are used to measure the CKM element $V_{cb}$, as such forming an important ingredient in the determination of e.g. the unitarity triangle; hence the question to which extent they can be affected by new physics contributions is important, specifically given the long-standing tension between $V_{cb}$ determinations from inclusive and exclusive decays and the significant hints for lepton flavour universality violation in $b\to cτν$ and $b\to s\ell\ell$ decays. We perform a comprehensive model-independent analysis of new physics in $b\to c\ellν$, considering all combinations of scalar, vector and tensor interactions occuring in single-mediator scenarios. We include for the first time differential distributions of $B\to D^*\ellν$ angular observables for this purpose. We show that these are valuable in constraining non-standard interactions. Specifically, the zero-recoil endpoint of the $B\to D\ellν$ spectrum is extremely sensitive to scalar currents, while the maximum-recoil endpoint of the $B\to D^*\ellν$ spectrum with transversely polarized $D^*$ is extremely sensitive to tensor currents. We also quantify the room for $e$-$μ$ universality violation in $b\to c\ellν$ transitions, predicted by some models suggested to solve the $b\to cτν$ anomalies, from a global fit to $B\to D\ellν$ and $B\to D^*\ellν$ for the first time. Specific new physics models, corresponding to all possible tree-level mediators, are also discussed. As a side effect, we present $V_{cb}$ determinations from exclusive $B$ decays, both with frequentist and Bayesian statistics, leading to compatible results. The entire numerical analysis is based on open source code, allowing it to be easily adapted once new data or new form factors become available.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

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