European Organization for Nuclear Research (CERN), Geneva, Switzerland.
Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
Phys Rev Lett. 2015 Aug 14;115(7):072001. doi: 10.1103/PhysRevLett.115.072001. Epub 2015 Aug 12.
Observations of exotic structures in the J/ψp channel, which we refer to as charmonium-pentaquark states, in Λ_{b}^{0}→J/ψK^{-}p decays are presented. The data sample corresponds to an integrated luminosity of 3 fb^{-1} acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/ψp mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380±8±29 MeV and a width of 205±18±86 MeV, while the second is narrower, with a mass of 4449.8±1.7±2.5 MeV and a width of 39±5±19 MeV. The preferred J^{P} assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
观测到 J/ψp 道中的奇异结构，我们称之为粲五夸克态，在 Λ_{b}^{0}→J/ψK^{-}p 衰变中。该数据样本对应于 LHCb 探测器在 7 TeV 和 8 TeV pp 碰撞中采集的 3 fb^{-1}积分亮度。对三体末态的振幅分析再现了双体质量和角分布。为了对 J/ψp 质量谱中看到的结构进行令人满意的拟合，需要包括两个描述共振态的 Breit-Wigner 振幅。这些共振的每个都具有超过 9 个标准偏差的显著性。一个的质量为 4380±8±29 MeV，宽度为 205±18±86 MeV，而第二个则更窄，质量为 4449.8±1.7±2.5 MeV，宽度为 39±5±19 MeV。首选的 J^{P}分配具有相反的宇称，一个状态具有自旋 3/2，另一个状态具有自旋 5/2。
