The $X(3872)$ resonance has been conjectured to be a $J^{PC}=1^{++}$ charm meson-antimeson two-body molecule. Meanwhile, there is no experimental evidence for larger, few-body compounds of multiple charm meson-antimeson pairs which would resemble larger molecules or nuclei. Here, we investigate such multimeson states to the extent of what can be deduced theoretically from essentials of the interaction between uncharged $D^0$ and $D^{*0}$ mesons. From a molecular $X(3872)$, we predict a $4X$ ($4^{++}$) octamer with a binding energy $B_{4X}>2.08\mathrm{MeV}$, assuming a $D^{*0}{\overline{D}}^0$ system close to the unitary limit [as suggested by the mass of the $X(3872)$]. If we consider heavy-quark spin symmetry explicitly, the $D^{*0}{\overline{D}}^{*0}$ ($2^{++}$) system is close to unitarity, too. In this case, we predict a bound $3X$ ($3^{++}$) hexamer with $B_{3X}>2.29\mathrm{MeV}$ and a more deeply bound $4X$ octamer with $B_{4X}>11.21\mathrm{MeV}$. These results exemplify with hadronic molecules a more general phenomenon of equal-mass two-species Bose systems composed of equal number of either type: the emergence of unbound four- and six-boson clusters in the limit of a short-range two-body interaction which acts only between bosons of different species. Finally, we also study the conditions under which a $2X$ ($2^{++}$) tetramer might form.

中文翻译：

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三重Xand超越：三个或更多X的强子系统（3872）

这 $X（3872）$ 共振被认为是一个 ${Ĵ}^{PC}={\mathrm{1个}}^{++}$魅力meson-antimeson两体分子。同时，没有实验证据表明类似多个更大的分子或核的，具有魅力的介子-反子对对的较大，少体的化合物。在这里，我们研究这种多介子态，其程度可以从理论上从不带电之间的相互作用的本质中推导出来。$d^0$ 和 $d^{*0}$介子。从分子$X（3872）$，我们预测 $4X$ （$4^{++}$）具有结合能的八聚体 ${乙}_{4X}>2.08\mathrm{电动汽车}$假设 $d^{*0}{\overline{d}}^0$ 接近单一极限的系统[如质量的建议 $X（3872）$]。如果我们明确考虑重夸克自旋对称性，$d^{*0}{\overline{d}}^{*0}$ （${\mathrm{2个}}^{++}$）系统也接近统一性。在这种情况下，我们预测$3X$ （$3^{++}$）六聚体 ${乙}_{3X}>2.29\mathrm{电动汽车}$ 和更深层次的约束 $4X$ octamer与 ${乙}_{4X}>11.21\mathrm{电动汽车}$。这些结果以强子分子为例，说明了由两种类型的均等数组成的等质量的两物种玻色系统的更普遍的现象：在短距离两体相互作用的极限内出现了未结合的四玻色子和六玻色子簇仅在不同物种的玻色子之间起作用。最后，我们还研究了$\mathrm{2个}X$ （${\mathrm{2个}}^{++}$）可能会形成四聚体。