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arXiv 2105.03399hep-phhep-exnucl-exnucl-th
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Cabibbo角反常下的类矢量轻子

Vector-like Leptons in Light of the Cabibbo-Angle Anomaly

Claudio Andrea Manzari

摘要:

Cabibbo-Cobayashi-Maskawa(CKM)矩阵的第一行显示了$\sim $ $3\,σ$与酉性的差异,称为“Cabibbo角度异常”(CAA)。这种紧张局势可以解释通过修改$W$耦合轻子,但为了始终评估这种解决方案的有效性,一个全球性的拟合,包括电弱(EW)的精度约束和低能量测试的轻子味普适性(LFU)是必要的。执行这样一个适合规范不变的6维算子,我们发现,即使假设LFU,包括CKM元素$V_{us}$和$V_{ud}$到电弱拟合有相关的影响,移动最佳拟合点显着。类矢量轻子(Vector-like lepton,VLL)是相应UV完成的主要候选者,因为它们可以影响已经在树水平上与轻子的$W$和$Z$耦合。研究由VLLs的六种可能表示(在SM规范群下)给出的新物理学(NP)的每种模式,我们发现任何单一表示最多比SM假设更好地描述实验数据。然而,允许在同一时间的几个表示的VLLs,我们发现一个简单的情况下,由一个单线态,$N$,耦合到电子和一个三线态,$Σ_1$,耦合到μ子,这不仅解释了CAA,但也提高了电弱拟合在这样一种方式,其最佳拟合点是首选的$4\,σ$相对于SM。

英文摘要:

The first row of the Cabibbo-Cobayashi-Maskawa (CKM) matrix shows a discrepancy of $\sim $$3\,σ$ with unitarity, known as the "Cabibbo Angle Anomaly" (CAA). This tension can be explained via modified $W$ couplings to leptons, but in order to consistently assess the validity of this solution, a global fit including the electroweak (EW) precision constraints and the low energy tests of lepton flavour universality (LFU) is necessary. Performing such a fit for gauge-invariant dimension-6 operators, we find that even when assuming LFU, including the CKM elements $V_{us}$ and $V_{ud}$ into the electroweak fit has a relevant impact, shifting the best fit point significantly. Vector-like leptons (VLLs) are prime candidates for a corresponding UV completion since they can affect the $W$ and $Z$ couplings to leptons already at tree-level. Studying each pattern of new physics (NP) given by the six possible representations of VLLs (under the SM gauge group) we find that any single representation describes experimental data at most slighlty better than the SM hypothesis. However, allowing for several representations of VLLs at the same time, we find a simple scenario consisting of a singlet, $N$, coupling to electrons and a triplet, $Σ_1$, coupling to muons which not only explains the CAA but also improves the electroweak fit in such a way that its best fit point is preferred by more than $4\,σ$ with respect to the SM.

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。

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