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arXiv 1703.06019hep-ph
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扭曲空间中$R_K$和$R_{D^{(*)}}$的轻子味普适性破坏

Lepton-flavor universality violation in $R_K$ and $R_{D^{(*)}}$ from warped space

Eugenio Megias, Mariano Quiros, Lindber Salas

备注：
40 pages, 20 figures; v2: Extended version with analyses of non-observation of FUV in the mu/e sector, LFU tests in tau decays, B->K nu nu and B->K tau tau; v3: Revised version where radiative corrections to observables $τ\to\ell νν$ and the $Z\bar\ell\ell$ couplings ($\ell=τ,μ$), as well as the LHC dilepton resonance from bottom-bottom fusion, are considered. Some conclusions changed
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摘要：

BaBar、LHCb和Belle合作组在过程$b\to s\ell\ell$（$\ell=μ,e$）和$b\to c \ell\barν_\ell$（$\ell=τ,μ,e$）中发现了一些异常，特别是在观测量$R_K$和$R_{D^{(\ast)}}$中，导致了可能的轻子味普适性违反。如果这些异常被证实，它们将不可避免地导致物理学超越标准模型。在本文中，我们试图容纳目前的异常在额外的维理论，解决的自然性问题的标准模型的手段与红外膜附近的一个强共形性破坏翘曲度规。如果左手底夸克和μ轻子在对偶理论中具有某种程度的复合性，那么$R_K$反常是可以接受的。这个理论与所有的电弱和味观测量是一致的，并且与卡鲁扎-克莱因电弱规范玻色子和胶子的所有直接搜索是一致的。费米子谱和费米子混合角可以用大多数基本右手底夸克、τ轻子和μ轻子重现。此外，$R_{D^{(\ast)}}$反常现象要求左手τ轻子具有很强的复合性，这与$g_{τ_L}^Z$耦合的实验数据相矛盾，可能除非在CKM矩阵的固定过程中引入某种程度的微调。

英文摘要：

Some anomalies in the processes $b\to s\ell\ell$ ($\ell=μ,e$) and $b\to c \ell\barν_\ell$ ($\ell=τ,μ,e$), in particular in the observables $R_K$ and $R_{D^{(\ast)}}$, have been found by the BaBar, LHCb and Belle Collaborations, leading to a possible lepton flavor universality violation. If these anomalies were confirmed they would inevitably lead to physics beyond the Standard Model. In this paper we try to accommodate the present anomalies in an extra dimensional theory, solving the naturalness problem of the Standard Model by means of a warped metric with a strong conformality violation near the infra-red brane. The $R_K$ anomaly can be accommodated provided that the left-handed bottom quark and muon lepton have some degree of compositeness in the dual theory. The theory is consistent with all electroweak and flavor observables, and with all direct searches of Kaluza-Klein electroweak gauge bosons and gluons. The fermion spectrum, and fermion mixing angles, can be reproduced by mostly elementary right-handed bottom quarks, and tau and muon leptons. Moreover the $R_{D^{(\ast)}}$ anomaly requires a strong degree of compositeness for the left-handed tau leptons, which turns out to be in tension with experimental data on the $g_{τ_L}^Z$ coupling, possibly unless some degree of fine-tuning is introduced in the fixing of the CKM matrix.

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