论文标题
LHCB double-j/ψ$频谱的耦合通道解释和附近的新状态的提示
Coupled-channel interpretation of the LHCb double-$J/ψ$ spectrum and hints of a new state near the $J/ψJ/ψ$ threshold
论文作者
论文摘要
最近，LHCB合作报告了在大型强子撞机上在质子 - 普罗顿碰撞中产生的$ j/ψ$ pairs的不变质谱中的明显结构。在这封信中，我们认为数据可以很好地描述在耦合通道方法的两个变体中，该方法采用$ t $ - amatrices与Unitarity一致：（i）只有两个频道，$ j/ψj/ψj/ψ$和$ψ$和$ψ（2s）J/ψ$，与这些通道相互依赖的$ j/cinters $ j/cinters $ j/cinters $ j/nin unchels/ly（II）允许的（II），或（II）。 $ψ（2s）J/ψ$和$ψ（3770）J/ψ$，只有恒定的触点交互。这两种配方都暗示在$ j/ψj/ψ$系统中存在带有量子数字$ j^{pc} = 0^{++} $或$ 2^{++} $的$ j/ψj/ψ$系统中的近阈值状态，我们称为$ x（6200）$。我们建议进行实验测试，以检查该状态的存在，并讨论需要在实验中研究哪些其他通道，以允许提出的两种机制之间进行独特的测试。如果通过三通道方法暗示的$ x（6200）$的分子性质得到了证实，那么许多其他双夸克状态应该由相同的结合机制驱动。特别是，应该有一个具有类似结合能的$η_Cη_C$分子。
Recently, the LHCb Collaboration reported pronounced structures in the invariant mass spectrum of $J/ψ$-pairs produced in proton-proton collisions at the Large Hadron Collider. In this Letter, we argue that the data can be very well described within two variants of a coupled-channel approach employing $T$-matrices consistent with unitarity: (i) with just two channels, $J/ψJ/ψ$ and $ψ(2S)J/ψ$, as long as energy-dependent interactions in these channels are allowed, or (ii) with three channels $J/ψJ/ψ$, $ψ(2S)J/ψ$ and $ψ(3770)J/ψ$ with just constant contact interactions. Both formulations hint at the existence of a near-threshold state in the $J/ψJ/ψ$ system with the quantum numbers $J^{PC}=0^{++}$ or $2^{++}$, which we refer to as $X(6200)$. We suggest experimental tests to check the existence of this state and discuss what additional channels need to be studied experimentally to allow for distinctive tests between the two mechanisms proposed. If the molecular nature of the $X(6200)$, as hinted by the three-channel approach, is confirmed, many other double-quarkonium states should exist driven by the same binding mechanism. In particular, there should be an $η_cη_c$ molecule with a similar binding energy.
