Revisiting the radiative decays J/psi -> gamma eta((')) in perturbative QCD
Revisiting the radiative decays J/psi -> gamma eta((')) in perturbative QCD
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重新审视微扰 QCD 中的辐射衰变 J/psi -> gamma eta(('))
DOI：
10.1016/j.nuclphysb.2019.114627
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发表时间：
2019
影响因子：
2.8
通讯作者：
Yang Ya Dong
中科院分区：
文献类型：
--
作者：
He Jun Kang;Yang Ya Dong
在微扰 QCD 的框架中，详细讨论了辐射衰变 J/ψ→ γ η (′)，其中所涉及的单环积分在保留轻夸克质量的情况下进行了分析评估。我们发现环积分之和对轻夸克质量不敏感，并且分支比 B (J/ψ→ γ η (′)) 几乎不依赖于 η (′) 分布幅度的形状。通过从低能过程中提取的 η− η′ 混合参数和 J/ψ→ γ η (′) 通过非微扰矩阵元素 < 0| G μ ν a G∼ a, μ ν| η (′)> 基于 U A (1) 异常优势论证，我们无法给出与实验结果一致的 R J/ψ 比值。然而，利用 BaBar 合作在 q 2= 112 GeV 2 测量的 γ⁎ γ− η′ 过渡形状因子中提取的参数，特别是混合角 phi= 33.5∘±0.9∘，我们得到 R J/ψ= 4.70，与 R J/ψ e x p= 4.65±0.21 非常吻合。作为交叉检查，使用 Γ e x p (η (′)→ γ γ) 和 J/ψ→ γ η (′) 的结果，我们得到 phi= 33.9∘±0.6∘。简要讨论了 Φ 测定之间的差异。
In the framework of perturbative QCD, the radiative decays J/ψ→ γ η (′) are revisited in detail, where the involved one-loop integrals are evaluated analytically with the light quark masses kept. We have found that the sum of loop integrals is insensitive to the light quark masses and the branching ratios B (J/ψ→ γ η (′)) barely depend on the shapes of η (′) distribution amplitudes. With the parameters of η− η′ mixing extracted from low energy processes and J/ψ→ γ η (′) by means of nonperturbative matrix elements< 0| G μ ν a G˜ a, μ ν| η (′)> based on U A (1) anomaly dominance argument, we could not give the ratio R J/ψ in agreement with experimental result. However, using the parameters, especially the mixing angle ϕ= 33.5∘±0.9∘, extracted from γ⁎ γ− η′ transition form factor measured at q 2= 112 GeV 2 by BaBar collaboration, we obtain R J/ψ= 4.70 in good agreement with R J/ψ e x p= 4.65±0.21. As a crossing check, with Γ e x p (η (′)→ γ γ) and our results for J/ψ→ γ η (′), we get ϕ= 33.9∘±0.6∘. The difference between the determinations of ϕ is briefly discussed.