摘要
The molecular positronium (sometimes also denoted as di-positronium) was the multi-electron bound state composed of e+e-e+e-,where the electromagnetic interaction is the underlying driving force.Although its existence was predicted as early as in1947[1],it remained elusive until it was produced experimentally in 2007[2].One may wonder whether there exists the analogue of the di-positronium in Quantum Chromodynamics,which is the tetraquark state with the flavor configurations cccc.Very recently,the LHCb Collaboration observed distinct structures with the cccc (two charm quarks and two anti-charm quarks) in the J/ψ w-pair mass spectrum[3].They reported a broad structure ranging from6.2 to 6.8 GeV and a narrow structure at around 6.9 GeV with a global significance of more than 5r.Let’s denote it as T4c.
作者
Kuang-Ta Chaoa
Shi-Lin Zhua
赵光达;朱世琳(School of Physics and State Key Laboratory of Nuclear Physics and Technology,Peking University,Beijing 100871,China;Center of High Energy Physics,Peking University,Beijing 100871,China)
基金
supported by the National Natural Science Foundation of China (11975033 and 11745006)。
