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arXiv 1608.04656hep-ph
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Zc（3900），Z（4430）和Xb（5568）态的四夸克结构

Four-quark structure of Zc(3900), Z(4430) and Xb(5568) states

Fabian Goerke, Thomas Gutsche, Mikhail A. Ivanov, Jurgen G. Korner, Valery E. Lyubovitskij, Pietro Santorelli

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14 pages
发表信息：
Phys. Rev. D 94, 094017 (2016)
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摘要：

我们研究了最近发现的带电$Z_c(3900)$，$Z(4430)$和$X_b(5568)$态的四夸克结构。在我们建立的协变夸克模型中计算了强衰变$Z_c^+ \to J/ψπ^+$（$η_cρ^+$，$\bar D^0D^{\ast\,+}$，$\bar D^{\ast\,0}D^+$），$Z(4430)^+ \to J/ψπ^+$（$ψ(2s) π^+$）和$X^+_b\to B_sπ^+$的宽度.我们发现文献中广泛使用的四夸克型电流的$Z_c(3900)$导致一个显着的抑制的$\bar D D^\ast$和$\bar D^\ast D$模式。与此相反，与BESIII协作组最近的实验数据一致，与$Z_c^+\to J/ψπ^+$、$η_cρ^+$模式相比，分子型电流为$\bar D D^\ast$模式提供了6-7倍的增强。在$Z(4430)$状态的情况下，我们测试了$Z(4430)^+ \to ψ(2s) π^+$和$Z(4430)^+ \to J/ψπ^+$衰减速率的比率$R_Z$对$Z(4430)$的尺寸参数$Λ_{Z(4430)}$的选择的灵敏度。利用LHCb合作组的数据推导出的这两个模式的总和的上限约束，我们发现，$R_Z$从4.64变化到4.08时，$Λ_{Z(4430)}$从2.2到3.2 GeV的变化。并对$Z(4430)^+ \to D^{\ast\,+} \bar D^{\ast\,0}$的衰变率进行了预测。

英文摘要：

We examine the four-quark structure of the recently discovered charged $Z_c(3900)$, $Z(4430)$, and $X_b(5568)$ states. We calculate the widths of the strong decays $Z_c^+ \to J/ψπ^+$ ($η_cρ^+$, $\bar D^0D^{\ast\,+}$, $\bar D^{\ast\,0}D^+$), $Z(4430)^+ \to J/ψπ^+$ ($ψ(2s) π^+$), and $X^+_b\to B_sπ^+$ within a covariant quark model previously developed by us. We find that the tetraquark-type current widely used in the literature for the $Z_c(3900)$ leads to a significant suppression of the $\bar D D^\ast$ and $\bar D^\ast D$ modes. Contrary to this a molecular-type current provides an enhancement by a factor of 6-7 for the $\bar D D^\ast$ modes compared with the $Z_c^+\to J/ψπ^+$, $η_cρ^+$ modes in agreement with recent experimental data from the BESIII Collaboration. In case of the $Z(4430)$ state we test a sensitivity of the ratio $R_Z$ of the $Z(4430)^+ \to ψ(2s) π^+$ and $Z(4430)^+ \to J/ψπ^+$ decay rates to a choice of the size parameter $Λ_{Z(4430)}$ of the $Z(4430)$. Using upper constraint for the sum of these two modes deduced from the LHCb Collaboration data we find that $R_Z$ varies from 4.64 to 4.08 when $Λ_{Z(4430)}$ changes from 2.2 to 3.2 GeV. Also we make the prediction for the $Z(4430)^+ \to D^{\ast\,+} \bar D^{\ast\,0}$ decay rate.

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