arXiv 1708.028692017-08hep-ph

准二体衰变$B \to η_c {(1S ,2S)}\;[ρ(770),ρ(1450),ρ(1700) \to ]\; ππ$的微扰QCD方法

Quasi-two-body decays $B \to η_c {(1S ,2S)}\;[ρ(770),ρ(1450),ρ(1700) \to ]\; ππ$ in the perturbative QCD approach

Ya Li, Ai-Jun Ma, Zhou Rui, Zhen-Jun Xiao

备注：: 10 pages, 3 figures
发表信息：: Nucl.Phys. B924 (2017) 745-758
DOI：: 10.1016/j.nuclphysb.2017.10.003

摘要：

本文用微扰QCD（PQCD）方法计算了准二体衰变$B \to η_c (1S ,2S)$ $[ρ(770), ρ(1450),ρ(1700)\to ] ππ$的分支比。考虑了来自$P$波共振$ρ(770)$、$ρ(1450)$和$ρ(1700)$的贡献。用矢量电流类时形状因子$F_π$对两π介子分布振幅$Φ_{ππ}^{\rm P}$进行参数化，研究了所考虑的衰变模式。我们发现：（a）PQCD对所考虑的准二体衰变的分支比的预言是$10^{-7} \sim 10^{-6}$量级的，而二体衰变率${\cal B}(B \to η_c{(1S,2S)} (ρ(1450),ρ(1700)))$是从相应的准二体衰变的分支比中提取出来的;（b）基于我们的理论结果，可以理解BABAR合作组测量的π介子形状因子平方$|F_π|^2$的整个模式;（c）确认了基于$B \to η_c ππ$和$B \to J/ψππ$衰变之间相似性的一般预期：$R_2(η_c)\approx 0.45$与测量的$R_2(J/ψ)\approx 0.56\pm 0.09$在误差范围内一致;以及（d）定义了所考虑的衰变模式的分支比之间的新比率$R_3(η_c(1S))$和$R_4(η_c(2S))$，并且可以通过未来的实验进行测试。

英文摘要：

In this paper, we calculated the branching ratios of the quasi-two-body decays $B \to η_c (1S ,2S)$ $[ρ(770), ρ(1450),ρ(1700)\to ] ππ$ by employing the perturbative QCD (PQCD) approach. The contributions from the $P$-wave resonances $ρ(770)$, $ρ(1450)$ and $ρ(1700)$ were taken into account. The two-pion distribution amplitude $Φ_{ππ}^{\rm P}$ is parameterized by the vector current time-like form factor $F_π$ to study the considered decay modes. We found that (a) the PQCD predictions for the branching ratios of the considered quasi-two-body decays are in the order of $10^{-7} \sim 10^{-6}$, while the two-body decay rates ${\cal B}(B \to η_c{(1S,2S)} (ρ(1450),ρ(1700)))$ are extracted from those for the corresponding quasi-two-body decays; (b) the whole pattern of the pion form factor-squared $|F_π|^2$ measured by the BABAR Collaboration could be understood based on our theoretical results; (c) the general expectation based on the similarity between $B \to η_c ππ$ and $B \to J/ψππ$ decays are confirmed: $R_2(η_c)\approx 0.45$ is consistent with the measured $R_2(J/ψ)\approx 0.56\pm 0.09$ within errors; and (d) new ratios $R_3(η_c(1S))$ and $R_4(η_c(2S))$ among the branching ratios of the considered decay modes are defined and could be tested by future experiments.

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。

摘要：

英文摘要：

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