Using proton-proton collision data at centre-of-mass energies of $\sqrt{s}=7,8$ and $13\mathrm{TeV}$ recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$, the invariant mass spectrum of J/ψ pairs is studied. A narrow structure around $6.9\text{GeV}/c^2$ matching the lineshape of a resonance and a broad structure just above twice the J/ψ mass are observed. The deviation of the data from nonresonant J/ψ-pair production is above five standard deviations in the mass region between $6.2$ and $7.4\mathrm{GeV}/c^2$, covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow $X\left(6900\right)$ structure are measured assuming a Breit-Wigner lineshape.

在质心能量处使用质子-质子碰撞数据$\sqrt{秒}=7,\mathrm{8个}$和$13\mathrm{电子伏特}$由大型强子对撞机的 LHCb 实验记录，对应于综合光度$9{\mathrm{面子书}}^{-\mathrm{1个}}$, 研究了J / ψ对的不变质谱。周围狭窄的结构$6.9\text{GeV}/C^{\mathrm{2个}}$观察到匹配共振的线形和刚好在J / ψ质量两倍以上的宽结构。数据与非共振J / ψ对产生的偏差在质量区域之间超过五个标准偏差$6.2$和$7.4\mathrm{GeV}/C^{\mathrm{2个}}$，涵盖了由四个魅力夸克组成的预测状态。狭窄的质量和自然宽度$X\left(6900\right)$假设 Breit-Wigner 线形来测量结构。