arXiv 1403.06352014-03hep-lathep-ph

用三味格点量子色动力学对零反冲$\bar{B}\to D^*\ell\barν$形状因子的$|V_{cb}|$修正

Update of $|V_{cb}|$ from the $\bar{B}\to D^*\ell\barν$ form factor at zero recoil with three-flavor lattice QCD

Jon A. Bailey, A. Bazavov, C. Bernard, C. M. Bouchard, C. DeTar, Daping Du, A. X. El-Khadra, J. Foley, E. D. Freeland, E. Gamiz, Steven Gottlieb, U. M. Heller, … 展开作者

Jon A. Bailey, A. Bazavov, C. Bernard, C. M. Bouchard, C. DeTar, Daping Du, A. X. El-Khadra, J. Foley, E. D. Freeland, E. Gamiz, Steven Gottlieb, U. M. Heller, A. S. Kronfeld, J. Laiho, L. Levkova, P. B. Mackenzie, E. T. Neil, Si-Wei Qiu, J. Simone, R. Sugar, D. Toussaint, R. S. Van de Water, Ran Zhou

备注：: 53 pages, 12 figures; expanded discussion of correlator fits, typos corrected, conforms to version published in PRD
发表信息：: Phys. Rev. D 89, 114504 (2014)
DOI：: 10.1103/PhysRevD.89.114504

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摘要：

我们用格点量子色动力学计算了半轻子衰变$\bar{B}^0\to D^{*+}\ell^-\barν$的零反冲形状因子（以及与同位旋和电荷共轭相关的模）.我们对轻价夸克和海夸克采用改进的交错作用量（MILC \asqtad \组态），对重夸克采用费米实验室作用量。与2008年的工作相比，我们的计算包含了更高的统计数据、更精细的晶格间距和更轻的夸克质量。作为调整新数据集的副产品，我们获得了$D_s$和$B_s$超精细分裂与几兆电子伏的精度。对于零反冲形状因子，我们得到$\mathcal{F}(1)=0.906(4)(12)$，其中第一个误差是统计的，第二个是所有系统误差的正交和。最新的HFAG平均的实验结果和QED效应的谨慎处理，我们发现$|V_{cb}| = (39.04 \pm 0.49_\text{expt} \pm 0.53_\text{QCD} \pm 0.19_\text{QED})\times10^{-3}$。QCD误差现在与实验误差相当。

英文摘要：

We compute the zero-recoil form factor for the semileptonic decay $\bar{B}^0\to D^{*+}\ell^-\barν$ (and modes related by isospin and charge conjugation) using lattice QCD with three flavors of sea quarks. We use an improved staggered action for the light valence and sea quarks (the MILC \asqtad\ configurations), and the Fermilab action for the heavy quarks. Our calculations incorporate higher statistics, finer lattice spacings, and lighter quark masses than our 2008 work. As a byproduct of tuning the new data set, we obtain the $D_s$ and $B_s$ hyperfine splittings with few-MeV accuracy. For the zero-recoil form factor, we obtain $\mathcal{F}(1)=0.906(4)(12)$, where the first error is statistical and the second is the sum in quadrature of all systematic errors. With the latest HFAG average of experimental results and a cautious treatment of QED effects, we find $|V_{cb}| = (39.04 \pm 0.49_\text{expt} \pm 0.53_\text{QCD} \pm 0.19_\text{QED})\times10^{-3}$. The QCD error is now commensurate with the experimental error.

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