arXiv 0707.26702007-07-18hep-ex

包含半轻子$\bar{B} \to X_{c} \ell^{-} \barν$衰变中强子质能谱矩的测量

Measurement of Moments of the Hadronic-Mass and -Energy Spectrum in Inclusive Semileptonic $\bar{B} \to X_{c} \ell^{-} \barν$ Decays

The BABAR Collaboration, B. Aubert

备注：: 21 pages, 11 postscript figures, submitted to EPS-HEP2007

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摘要：

本文给出了半轻子$\bar{B} \to X_{c} \ell^{-} \barν$衰变中包含强子质量和能量谱的矩的测量。这项研究是基于一个样本的2.32亿$Υ(4S) \to B\bar{B}$衰变记录的BABAR探测器在PEP-II $e^+e^-$储存环。我们重建的半轻子衰变识别轻子的事件标记的第二$B$介子的强子衰变完全重建。我们报告了在$B$ -介子静止坐标系中测量的不同的最小轻子动量在0.8和$1.9 \mathrm{GeV}/c$之间时，$<m_X^k>$与$k=1,...,6$和$<n_X^k>$与$k=2,4,6$和$n_X^2 = m_X^2 c^4 - 2 \tildeΛ E_X + \tildeΛ^2$的矩的初步结果，其中$m_X$是强子系统的质量，$E_X$是能量，$\tildeΛ$是$0.65 \mathrm{GeV}$的常数。这些预测的框架中的重夸克展开（HQE），它允许提取的总半轻子分支分数，CKM矩阵元素$|V_{cb}|$，夸克质量$m_b$和$m_c$，连同占主导地位的非微扰HQE参数。作为初步结果，我们发现了$|V_{cb}| = (41.88 \pm 0.81) \cdot 10^{-3}$和$m_b = (4.552 \pm 0.055) \mathrm{GeV}/c^2$。

英文摘要：

We present a measurement of moments of the inclusive hadronic-mass and -energy spectrum in semileptonic $\bar{B} \to X_{c} \ell^{-} \barν$ decays. This study is based on a sample of 232 million $Υ(4S) \to B\bar{B}$ decays recorded by the BABAR detector at the PEP-II $e^+e^-$-storage rings. We reconstruct the semileptonic decay by identifying a lepton in events tagged by a fully reconstructed hadronic decay of the second $B$ meson. We report preliminary results for the moments $<m_X^k>$ with $k=1,...,6$ and $<n_X^k>$ with $k=2,4,6$ and $n_X^2 = m_X^2 c^4 - 2 \tildeΛ E_X + \tildeΛ^2$, with $m_X$ the mass of the hadronic system, $E_X$ its energy, and $\tildeΛ$ a constant of $0.65 \mathrm{GeV}$, for different minimal lepton momenta between 0.8 and $1.9 \mathrm{GeV}/c$ measured in the $B$-meson rest frame. These are predicted in the framework of a Heavy Quark Expansion (HQE), which allows the extraction of the total semileptonic branching fraction, the CKM-matrix element $|V_{cb}|$, and the quark masses $m_b$ and $m_c$, together with the dominant non-perturbative HQE parameters. We find as preliminary results $|V_{cb}| = (41.88 \pm 0.81) \cdot 10^{-3}$ and $m_b = (4.552 \pm 0.055) \mathrm{GeV}/c^2$.

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