北京正负电子对撞机上的粲夸克偶素物理实验研究

Experimental Study on Charmonium Physics at Beijing Electron-Positron Collider

北京谱仪合作组在北京正负电子对撞机上采集了世界上最大的Ψ(2S)粒子数据样本,开展了粲夸克偶素物理的广泛研究。测量了粲阈下全部6个已知粲夸克偶素涉及质量、宽度和衰变分支比等的大批重要参数,其中21项为国际首次测量,相当一部分结果具有国际最高精度,51项数据被收入国际权威性文献《粒子物理评论》(2000年版)。通过对Ψ(2S)和J/Ψ数据的比较研究,在若干种遍举强衰变的末志介子模式中,观察到了一系列反常现象,挑战常规理论图象,引发了深入探讨粲夸克偶素衰变机制的新的一轮理论努力。有关实验结果应用于粒子物理实验与理论研究的若干方面,揭示出多项重要物理性质。

Charmonium is a superb laboratory for the study of Quantum Chromodynamics, the theory of the strong interactions in Standard Model of particle physics. Using the world's largest sample of ψ(2S) events, extensive studies on all 6 charmonium states below charm threshold have been conducted by the Beijing Spectrometer Collaboration at the Beijing Electron-Positron Collider. Of the numerous results including masses, widths and branching fractions. 21 data are measured for the first time, a large part of the others have the highest precision, and 51 measurements in all are included in the 2000 edition of Review of Particle Physics. A number of anomalies have been observed from a careful comparison of the branching tractions for various modes of exclusive hadronic decays of the J/ψand ψ (2S). This poses significant challenges to the present understanding of charmonium decays and stimulates a new round of efforts to resolve the puzzles. Implications of the experimental data have been widely explored; several important physics properties are revealed.