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arXiv 1402.2849hep-ph
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包含$B\to X_clν$衰变矩测量对排斥分支分数$BF_i(B^+\to X_c^il^+ν)$的约束

Constraints on exclusive branching fractions $BF_i(B^+\to X_c^il^+ν)$ from moment measurements in inclusive $B\to X_clν$ decays

Florian U. Bernlochner, Dustin Biedermann, Heiko Lacker, Thomas Lück

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57 pages, 28 figures, 23 tables
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摘要：

作为一种替代直接测量，我们提取独家分支部分半轻子B介子衰变到粲介子，$BF_i(B\to X_c^ilν)$与$X_c^i = D, D^*, D_0, D'_1, D_1, D_2, D', D'^*$和非共振的最终状态$(D^{(*)}π)_{nr}$，从一个适合的电子能量，强子质量和组合强子质能矩测量包容$B\to X_clν$衰变。通过将排他性支化分数的总和约束到$BF(B\to X_clν)$的测量值，并且对于直接测量的支化分数使用不同的附加约束项集合来进行拟合。不存在单独增强单个分支分数以缩小$BF(B\to X_clν)$与已知分支分数之和$BF_i(B\to X_c^ilν)$之间的差距的拟合情形。拟合的$BF(B\to D^*lν)$比直接测量值大5%至10%，这取决于$BF(B\to D^*lν)$是否被限制为其直接测量值。$BF(B\to Dlν)$值与直接测量值一致，除非$BF(B\to D^*lν)$受到限制，这会导致$BF(B\to Dlν)$值更高。在较大的不确定性范围内，$BF(B\to D'_1lν)$与直接测量结果一致。根据拟合情况，$BF(B\to D_0lν)$与其直接测量值一致或大于其直接测量值。拟合不能容易地解开$B\to D_1lν$和$B\to D_2lν$，并且倾向于增加这两个分支分数的总和。发现具有非共振$(D^{(*)}π)_{nr}$终态的$BF(B\to (D^{(*)}π)_{nr}lν)$为0.2- 0.4%，与$B\to D^{(*)}πlν$和$B\to D^{**}(D^{(*)}π)lν$测量一致。假设$D'$和$D'^*$可以分别用观测到的$D(2550)$和$D^*(2600)$状态识别，则没有发现迄今为止未测量的$B\to D'^{(*)}lν$衰变的显著贡献的迹象。

英文摘要：

As an alternative to direct measurements, we extract exclusive branching fractions of semileptonic B-meson decays to charmed mesons, $BF_i(B\to X_c^ilν)$ with $X_c^i = D, D^*, D_0, D'_1, D_1, D_2, D', D'^*$ and non-resonant final states $(D^{(*)}π)_{nr}$, from a fit to electron energy, hadronic mass and combined hadronic mass-energy moments measured in inclusive $B\to X_clν$ decays. The fit is performed by constraining the sum of exclusive branching fractions to the measured value of $BF(B\to X_clν)$, and with different sets of additional constraining terms for the directly measured branching fractions. There is no fit scenario in which a single branching fraction alone is enhanced to close the gap between $BF(B\to X_clν)$ and the sum of known branching fractions $BF_i(B\to X_c^ilν)$. The fitted $BF(B\to D^*lν)$ is 5% to 10% larger than the direct measurement depending on whether or not $BF(B\to D^*lν)$ is constrained to its direct measurement. $BF(B\to Dlν)$ values are in good agreement with the direct measurement unless $BF(B\to D^*lν)$ is constrained, which results in a higher $BF(B\to Dlν)$ value. Within large uncertainties, $BF(B\to D'_1lν)$ agrees with direct measurements. Depending on the fit scenario, $BF(B\to D_0lν)$ is consistent with or larger than its direct measurement. The fit is not able to easily disentangle $B\to D_1lν$ and $B\to D_2lν$, and tends to increase the sum of these two branching fractions. $BF(B\to (D^{(*)}π)_{nr}lν)$ with non-resonant $(D^{(*)}π)_{nr}$ final states is found to be 0.2-0.4%, consistent with $B\to D^{(*)}πlν$ and $B\to D^{**}(D^{(*)}π)lν$ measurements. No indication is found for significant contributions from so far unmeasured $B\to D'^{(*)}lν$ decays assuming that the $D'$ and $D'^*$ can be identified with the observed $D(2550)$, respectively, $D^*(2600)$ state.

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