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arXiv 1509.01249hep-ph
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从U(2)味模型研究B介子衰变的轻子味非普适性

Lepton Flavor Non-Universality in B-meson Decays from a U(2) Flavor Model

Adam Falkowski, Marco Nardecchia, Robert Ziegler

摘要:

我们利用基于$U(2)$味对称性的费米子质量模型讨论了最近半轻子$B$介子衰变中的反常现象。对$b \to s \ell \ell$跃迁的新贡献是由于$Z^\prime$矢量玻色子的树级交换而产生的,该矢量玻色子测量味对称性的$U(1)$子群。它们由单个参数控制,并且与标准模型预测大致对齐,其中在$e$通道中具有相长干涉,在$μ$通道中具有相消干涉。在不违反夸克和轻子扇区味破坏的现有约束的情况下,可以很好地再现当前半轻子$B$ -介子衰变的实验数据。我们的模型将通过对$b \to s \ell \ell$跃迁的新测量以及未来的电弱精确测试、直接$Z^\prime$搜索和$μ$ - $e$在核中的转换进行测试。

英文摘要:

We address the recent anomalies in semi-leptonic $B$-meson decays using a model of fermion masses based on the $U(2)$ flavor symmetry. The new contributions to $b \to s \ell \ell$ transitions arise due to a tree-level exchange of a $Z^\prime$ vector boson gauging a $U(1)$ subgroup of the flavor symmetry. They are controlled by a single parameter and are approximately aligned to the Standard Model prediction, with constructive interference in the $e$-channel and destructive interference in the $μ$-channel. The current experimental data on semi-leptonic $B$-meson decays can be very well reproduced without violating existing constraints from flavor violation in the quark and lepton sectors. Our model will be tested by new measurements of $b \to s \ell \ell$ transitions and also by future electroweak precision tests, direct $Z^\prime$ searches, and $μ$-$e$ conversion in nuclei.

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