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arXiv 1702.07356hep-ph
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$Υ$和$ψ$轻子衰变作为解决$R_D^{(*)}$难题的探针

$Υ$ and $ψ$ leptonic decays as probes of solutions to the $R_D^{(*)}$ puzzle

Daniel Aloni, Aielet Efrati, Yuval Grossman, Yosef Nir

摘要:

比率$R(D^{(*)})\equiv\frac{Γ(B\to D^{(*)}τν)}{Γ(B\to D^{(*)}\ellν)}$($\ell=e,μ$)的实验测量显示$3.9σ$偏离标准模型预测。在没有轻右手中微子的情况下,对$b\to cτν$衰变的新物理贡献必然也会修改$b\bar b\toτ^+τ^-$和/或$c\bar c\toτ^+τ^-$跃迁。这些贡献导致违反轻子味普适性,分别在$Υ$和$ψ$轻子衰变。我们分析了测量轻子矢量介子衰变对解决$R(D^{(*)})$难题的约束。来自BaBar和Belle的可用数据已经不利于这种异常现象的一些新物理解释。通过在即将到来的Belle II实验中测量$Υ(1S,2S,3S)\toττ$可以进行进一步的区分。

英文摘要:

Experimental measurements of the ratios $R(D^{(*)})\equiv\frac{Γ(B\to D^{(*)}τν)}{Γ(B\to D^{(*)}\ellν)}$ ($\ell=e,μ$) show a $3.9σ$ deviation from the Standard Model prediction. In the absence of light right-handed neutrinos, a new physics contribution to $b\to cτν$ decays necessarily modifies also $b\bar b\toτ^+τ^-$ and/or $c\bar c\toτ^+τ^-$ transitions. These contributions lead to violation of lepton flavor universality in, respectively, $Υ$ and $ψ$ leptonic decays. We analyze the constraints resulting from measurements of the leptonic vector-meson decays on solutions to the $R(D^{(*)})$ puzzle. Available data from BaBar and Belle can already disfavor some of the new physics explanations of this anomaly. Further discrimination can be made by measuring $Υ(1S,2S,3S)\toττ$ in the upcoming Belle II experiment.

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