A highly significant structure is observed in the ${\mathrm{\Lambda }}_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ mass spectrum, where the ${\mathrm{\Lambda }}_c^{+}$ baryon is reconstructed in the decay mode $p{K}^{-}{\pi }^{+}$. The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon ${\mathrm{\Xi }}_{cc}^{++}$. The difference between the masses of the ${\mathrm{\Xi }}_{cc}^{++}$ and ${\mathrm{\Lambda }}_c^{+}$ states is measured to be $1334.94\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\mathrm{MeV}/c^2$, and the ${\mathrm{\Xi }}_{cc}^{++}$ mass is then determined to be $3621.40\pm 0.72(\text{stat.})\pm 0.27(\text{syst}\mathrm{.})\pm 0.14({\mathrm{\Lambda }}_c^{+})\mathrm{MeV}/c^2$, where the last uncertainty is due to the limited knowledge of the ${\mathrm{\Lambda }}_c^{+}$ mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $1.7{\mathrm{fb}}^{-1}$, and confirmed in an additional sample of data collected at 8 TeV.

中文翻译：

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双重迷惑的重子的观察++ cc ++

观察到一个非常重要的结构 ${\mathrm{\Lambda }}_C^{+}{ķ}^{-}{\pi }^{+}{\pi }^{+}$ 质谱图 ${\mathrm{\Lambda }}_C^{+}$ 重子以衰减模式重建 $p{ķ}^{-}{\pi }^{+}$。该结构与源自弱衰变的粒子（被鉴定为双倍迷人的重子）一致${\mathrm{\Xi }}_{CC}^{++}$。群众之间的区别${\mathrm{\Xi }}_{CC}^{++}$ 和 ${\mathrm{\Lambda }}_C^{+}$ 状态被测量为 $1334.94\pm 0.72（\text{统计资料。}）\pm 0.27（\text{系统}\mathrm{。}）\mathrm{电动汽车}/C^{\mathrm{2个}}$和 ${\mathrm{\Xi }}_{CC}^{++}$ 然后确定质量为 $3621.40\pm 0.72（\text{统计资料。}）\pm 0.27（\text{系统}\mathrm{。}）\pm 0.14（{\mathrm{\Lambda }}_C^{+}）\mathrm{电动汽车}/C^{\mathrm{2个}}$，最后的不确定性是由于对知识的了解有限 ${\mathrm{\Lambda }}_C^{+}$大量的。在LHCb实验收集的质子-质子碰撞数据样本中，以13 TeV的质心能量观察到该状态，这对应于$1.7{\mathrm{fb}}^{-\mathrm{1个}}$，并在以8 TeV收集的其他数据样本中得到确认。