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arXiv 1503.05388hep-lathep-ph
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使用$\hat{B}_K$和$V_{cb}$的格点量子色动力学输入的$\varepsilon_K$的标准模型评估

Standard Model evaluation of $\varepsilon_K$ using lattice QCD inputs for $\hat{B}_K$ and $V_{cb}$

Jon A. Bailey, Yong-Chull Jang, Weonjong Lee, Sungwoo Park

备注：
20 pages, 3 figures, references augmented, typos fixed
发表信息：
Phys. Rev. D 92, 034510 (2015)
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摘要：

我们报告了间接CP破坏参数$\varepsilon_K$的标准模型评估，使用从格点量子色动力学确定的输入：来自$K_{\ell 3}$和$K_{μ2}$衰变的K介子袋参数$\hat{B}_K$，$ξ_0$，$|V_{us}|$，以及来自零反冲下排他性衰变$\bar{B} \to D^* \ell \barν$的轴向电流形状因子的$|V_{cb}|$。对$\varepsilon_K$的理论表达式进行了全面的回顾，给出了忽略修正的大小的估计，包括长距离效应。通过盒形图的短距离贡献进入的CKM矩阵元素采用Wolfenstein参数化$(|V_{cb}|, λ, \barρ, \barη)$。对于中心值，我们从UTfit协作的仅角度拟合中获取酉三角形顶点$(\barρ, \barη)$，并使用$V_{us}$作为独立输入来修复$λ$。我们发现，用$3.4σ$的标准模型预言的$\varepsilon_K$（格点量子色动力学结果）低于实验值。然而，在包含$V_{cb}$（重夸克展开的结果）的情况下，$\varepsilon_K$的标准模型预测与其实验值之间没有差距。对于$\varepsilon_K$的计算，我们执行重正化群运行以获得次-前导阶的$η_{cc}$;我们发现$η_{cc}^\mathrm{NNLO}=1.72(27)$。

英文摘要：

We report the Standard Model evaluation of the indirect CP violation parameter $\varepsilon_K$ using inputs determined from lattice QCD: the kaon bag parameter $\hat{B}_K$, $ξ_0$, $|V_{us}|$ from the $K_{\ell 3}$ and $K_{μ2}$ decays, and $|V_{cb}|$ from the axial current form factor for the exclusive decay $\bar{B} \to D^* \ell \barν$ at zero-recoil. The theoretical expression for $\varepsilon_K$ is thoroughly reviewed to give an estimate of the size of the neglected corrections, including long distance effects. The Wolfenstein parametrization $(|V_{cb}|, λ, \barρ, \barη)$ is adopted for CKM matrix elements which enter through the short distance contribution of the box diagrams. For the central value, we take the Unitarity Triangle apex $(\barρ, \barη)$ from the angle-only fit of the UTfit collaboration and use $V_{us}$ as an independent input to fix $λ$. We find that the Standard Model prediction of $\varepsilon_K$ with exclusive $V_{cb}$ (lattice QCD results) is lower than the experimental value by $3.4σ$. However, with inclusive $V_{cb}$ (results of the heavy quark expansion), there is no gap between the Standard Model prediction of $\varepsilon_K$ and its experimental value. For the calculation of $\varepsilon_K$, we perform the renormalization group running to obtain $η_{cc}$ at next-to-next-to-leading-order; we find $η_{cc}^\mathrm{NNLO}=1.72(27)$.

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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