arXiv 1506.017052015-06hep-ph

关于B衰变中轻子味普适性的破缺

On the breaking of Lepton Flavor Universality in B decays

Admir Greljo, Gino Isidori, David Marzocca

备注：: 20 pages, 7 figures. v2: discussion on flavor structure clarified; added discussion on the associated production of the heavy vectors and a few refs. Published version

摘要：

鉴于最近的实验表明违反轻子味普适性（LFU）在$B$衰变，我们分析的限制和影响LFU相互作用，既使用有效的理论方法，和一个明确的动力学模型。我们表明，一个简单的动力学模型的基础上的$SU(2)_L$三重大质量矢量玻色子，主要耦合到第三代费米子（夸克和轻子），可以显着提高目前的数据的描述。特别是，该模型降低了数据和SM预测之间的张力，涉及：i）$B\to D^{(*)} \ell ν$衰变中$τ$ - $μ$普适性的破坏; ii）$B \to K \ell^+\ell^-$衰变中$μ$ - $e$普适性的破坏; iii）$|V_{cb}|$和$|V_{ub}|$的排他性和包容性测定之间的差异。该模型的最小版本与ATLAS和CMS直接搜索新的质量向量（衰减为$τ^+τ^-$对）处于紧张状态，但这种紧张可以通过额外的非标准自由度来减少。进一步预测的模型在低能量和高能量，鉴于未来的高统计数据，进行了讨论。

英文摘要：

In view of recent experimental indications of violations of Lepton Flavor Universality (LFU) in $B$ decays, we analyze constraints and implications of LFU interactions, both using an effective theory approach, and an explicit dynamical model. We show that a simple dynamical model based on a $SU(2)_L$ triplet of massive vector bosons, coupled predominantly to third generation fermions (both quarks and leptons), can significantly improve the description of present data. In particular, the model decreases the tension between data and SM predictions concerning: i) the breaking of $τ$-$μ$ universality in $B\to D^{(*)} \ell ν$ decays; ii) the breaking of $μ$-$e$ universality in $B \to K \ell^+\ell^-$ decays; iii) the difference between exclusive and inclusive determinations of $|V_{cb}|$ and $|V_{ub}|$. The minimal version of the model is in tension with ATLAS and CMS direct searches for the new massive vectors (decaying into $τ^+τ^-$ pairs), but this tension can be decreased with additional non-standard degrees of freedom. Further predictions of the model both at low- and high-energies, in view of future high-statistics data, are discussed.

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