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arXiv 1408.2297hep-ph
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背景场中QCD理论中的重赝标超前扭转分布振幅

Heavy Pseudoscalar Leading-Twist Distribution Amplitudes within QCD Theory in Background Fields

Tao Zhong, Xing-Gang Wu, Tao Huang

备注：
14 pages, 14 figures
发表信息：
Eur.Phys.J. C75 (2015) 2, 45
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摘要：

本文在QCD理论的背景场中研究了重赝标量（HPs），如$η_c$，$η_b$和$B_c$的首扭分布振幅（DA）。新的总和规则，以六维凝聚的HP衰减常数和他们的领先扭转DA时刻。从HP衰变常数的求和规则，我们得到了$f_{η_c} = 453 \pm 4 \textrm{MeV}$、$f_{B_c} = 498 \pm 14 \textrm{MeV}$和$f_{η_b} = 811 \pm 34 \textrm{MeV}$。基于HPs首扭DA矩的求和规则，我们构造了一个新的$η_c$、$η_b$和$B_c$首扭DA矩的模型。我们目前的HP DA模型也可以适用于轻伪标DA，例如pion和kaon DA。因此，它应适用于广泛的QCD排他性过程。作为应用，我们应用$η_c$导扭DA计算了$B_c \to η_c$跃迁形状因子$f_+^{B_c \to η_c}(q^2)$。在最大反冲区，我们得到了$f_+^{B_c \to η_c}(0) = 0.612^{+0.053}_{-0.052}$。在进一步外推TFF $f_+^{B_c \to η_c}(q^2)$到其允许的$q^2$区域后，我们预测了半轻子衰变$B_c \to η_c l ν$的分支比。我们得到了无质量轻子的${\cal B}(B_c \to η_c l ν)=\left(7.70^{+1.65}_{-1.48}\right) \times 10^{-3}$，这与文献中得到的LCSR估计是一致的。

英文摘要：

In this paper, we study the leading-twist distribution amplitude (DA) of the heavy pseudoscalars (HPs), such as $η_c$, $η_b$ and $B_c$, within the QCD theory in the background fields. New sum rules up to dimension-six condensates for both the HP decay constants and their leading-twist DA moments are presented. From the sum rules for the HP decay constants, we obtain $f_{η_c} = 453 \pm 4 \textrm{MeV}$, $f_{B_c} = 498 \pm 14 \textrm{MeV}$, and $f_{η_b} = 811 \pm 34 \textrm{MeV}$. Basing on the sum rules for the HPs' leading-twist DA moments, we construct a new model for the $η_c$, $η_b$ and $B_c$ leading-twist DAs. Our present HP DA model can also be adaptable for the light pseudo-scalar DAs, such as the pion and kaon DAs. Thus, it shall be applicable for a wide range of QCD exclusive processes. As an application, we apply the $η_c$ leading-twist DA to calculate the $B_c \to η_c$ transition form factor $f_+^{B_c \to η_c}(q^2)$. At the maximum recoil region, we obtain $f_+^{B_c \to η_c}(0) = 0.612^{+0.053}_{-0.052}$. After further extrapolating the TFF $f_+^{B_c \to η_c}(q^2)$ to its allowable $q^2$ region, we predict the branching ratio for the semi-leptonic decay $B_c \to η_c l ν$. We obtain ${\cal B}(B_c \to η_c l ν)=\left(7.70^{+1.65}_{-1.48}\right) \times 10^{-3}$ for massless leptons, which is consistent with the LCSRs estimation obtained in the literature.

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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