Sci Bull (Beijing). 2021 Jul 15;66(13):1278-1287. doi: 10.1016/j.scib.2021.02.030. Epub 2021 Mar 9.
First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξ→J/ψΛK decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9MeV and 17.3±6.5MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ states, Ξ1690 and Ξ1820, are seen for the first time in a Ξ decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.
通过对Ξ→J/ψΛK衰变进行振幅分析，首次在J/ψΛ不变质量分布中获得了结构证据。观察到的结构与具有奇异数的粲偶素五夸克相符，其显著性为3.1σ，包括系统不确定性和“看别处效应”。其质量和宽度分别确定为4458.8±2.9MeV和17.3±6.5MeV，其中所引用的不确定性为统计和系统不确定性。该结构也与由两个共振组成相符。此外，窄激发态Ξ，即Ξ1690和Ξ1820，首次在Ξ衰变中被观测到，并且它们的质量和宽度以更高的精度被测量。该分析使用了与9 fb的总积分亮度相对应的质子-质子碰撞数据，这些数据是在大型强子对撞机底夸克实验中，在质心能量为7、8和13 TeV时收集的。
