arXiv 1406.77822014-06hep-ph

$B\to ρ$半轻子衰变和$|V_{ub}|$

$B\to ρ$ semileptonic decays and $|V_{ub}|$

C. Albertus, E. Hernández, J. Nieves

备注：: 13 latex pages, 3 figures, 3 tables. We have corrected a misinterpretation of experimental data on partial branching fractions. Results are modified but main conclusion remains the same
发表信息：: Physical Review D 90, 013017 (2014); erratum Physical Review D 90, 079906 (2014)
DOI：: 10.1103/PhysRevD.90.013017

摘要：

我们重新评估的$B\toρ\,l^+ν_l$衰变宽度作为一个完整的$B\toππ\,l^+ν_l$四粒子衰变，其中两个最后的π介子通过中间$ρ$介子产生。衰减宽度可以写为离壳$ρ$的$B\toρ\,l^+ν_l$衰减宽度与$ρ\toππ$线形的卷积。这允许完全纳入有限$ρ$介子宽度的影响。如图所示，考虑$ρ$介子宽度效应使$|V_{ub}|$值增加约8%，使其与基于$B\toπ$衰变的测定结果更好地一致。我们从一个色散的Omnès表示中得到了$B\to ρ$半轻子形状因子的$q^2$依赖性。Omnès减法常数和整体归一化参数$|V_{ub}|$分别在低和高$q^2$区域与光锥求和规则和格点QCD理论形状因子计算相拟合，并与CLEO、BaBar和Belle实验部分分支分数分布相拟合.从该全局拟合中提取的值为$|V_{ub}|=(3.12\pm 0.13)\times 10^{-3}$，与粒子数据组引用的平均$B\to π$独占值$|V_{ub}|=(3.23\pm 0.31)\times 10^{-3}$一致。如果仅使用最新的Belle Collaboration数据，则提取的值将增加到$|V_{ub}|=(3.51\pm 0.16)\times 10^{-3}$。后一个值与基于$B\toπ$半轻子衰变的不同理论确定以及CKMfitter和UTfit组获得的值一致。在任何情况下，与从包含半轻子$b\to u$衰变中提取的$|V_{ub}|$值的明显张力仍然存在。

英文摘要：

We reevaluate the $B\toρ\,l^+ν_l$ decay width as a full $B\toππ\,l^+ν_l$ four-particle decay, in which the two final pions are produced via an intermediate $ρ$ meson. The decay width can be written as a convolution of the $B\toρ\,l^+ν_l$ decay width, for an off-shell $ρ$, with the $ρ\toππ$ line shape. This allows to fully incorporate the effects of the finite $ρ$ meson width. As shown, consideration of the $ρ$ meson width effects increase the $|V_{ub}|$ value by some 8%, rendering it in better agreement with the determination based in the $B\toπ$ decay. We take the $q^2$ dependence of the $B\to ρ$ semileptonic form factors from a dispersive Omnès representation. The Omnès subtraction constants and the overall normalization parameter $|V_{ub}|$ are fitted to light cone sum rules and lattice QCD theoretical form-factor calculations, in the low and high $q^2$ regions respectively, together to the CLEO, BaBar and Belle experimental partial branching fraction distributions. The extracted value from this global fit is $|V_{ub}|=(3.12\pm 0.13)\times 10^{-3}$, in agreement with the average $B\to π$ exclusive value $|V_{ub}|=(3.23\pm 0.31)\times 10^{-3}$ quoted by the Particle Data Group. The extracted value increases to $|V_{ub}|=(3.51\pm 0.16)\times 10^{-3}$ if only the most recent Belle Collaboration data is used. This latter value is in agreement with different theoretical determinations based in the $B\toπ$ semileptonic decay and the values obtained by the CKMfitter and UTfit groups. In any case a clear tension with the $|V_{ub}|$ value extracted from inclusive semileptonic $b\to u$ decays still persists.

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