北京谱仪III实验上轻介子衰变研究

The project leader has much experience in the experimental particle physics. At BESII experiment, I made substantial contributions to search for the new forms of particles, in particular in the discovery of X(1835) particle. At the ZEUS experiment in Germany, I measured the charm fragmentation function in the photoproduction using the HERAI data and finished the Monte Carlo realization of the Calorimeter at the ZEUS detector. As the convener of the light hadron spectroscopy group, I am now is focusing on the study of light hadron spectroscopy at BESIII experiment. Many significant progresses on the search for new light hadrons and η/η′physics were achieved in recent years.. We made a survey on the current status of the pseudoscalar meson and vector meson and found that the further study on the light pseudoscalar and vector mesons are strongly needed. With the world’s largest data samples of J/psi and Psi(2S) collected at the BESIII detector, we propose to perform an extensive study on the light pseudoscalar and vector mesons, as well as their excited states, to study their decay dynamics, which provide much useful information to test the effective theory at the low energy region and hence to deepen our understanding on the structure of light hadrons and hadronic interactions. For study of the pseudoscalar mesons, we mainly focus on the Dalitz plot analysis ofη/η′decays, the extract of p-wave contribution in η′->3π, search forη(1295) in charmonium decays and study of η(1405) decay dynamics. While for the vector mesons, we first perform the Dalitz plot analysis of omega->3π to check the final state interaction contribution and to test the dispersive theory. With the Partial Wave Analysis (PWA), the decay of J/psi->omega ηπ will be analyzed to study the omega excited states, e.g., omega(1420) and omega(1650). In addition, we suggest to analyze J/psi-->pi+pi-pi0 to figure out the contribution from rho(770) excited states. At last we will investigate the a0(980)-f0(980) mixing by analyzing the decays of J/psi-->phi eta pi0 and Chi-c1--> pi+pi-pi0, and then provide the experimental proof on this issue.

申请人长期从事高能物理实验,研究曾参加北京谱仪II实验和德国ZEUS实验。在BESII实验发现X(1835)新粒子过程中做出了突出贡献，并获得国家自然科学二等奖(排名第三)；目前主要从事轻强子谱及新强子态寻找等研究工作，并取得许多重要成果。..本项目提出利用BESIII实验所获取的数据，系统研究轻介子衰变，分析它们的衰变特性，检验低能区强相互作用理论，解决轻介子研究领域一些长期悬而未决的问题，加深我们对轻介子结构的认识。对于赝标量介子，主要研究η/η′的达利兹图分析，η(1295)的存在与否和η(1405)的衰变性质等。对于矢量介子，主要研究 omega->3π中末态相互作用的贡献，检验色散理论，同时对omega 和rho的激发态进行研究；对于标量介子，深入开展a0(980)-f0(980)混合研究，提出两者之间是否混合的确切证据。

轻介子衰变是研究低能区强相互作用的重要手段，对检验低能区有效理论模型，确定形状因子及检验基本对成性都起着非常重要的作用。由于粲偶素衰变中含有大量轻介子，北京谱仪III实验上所采集的高统计量数据为研究轻介子衰变提供了独一无二的机会。. 利用北京谱仪III实验上采集的高统计量J/psi和Psi(2S)事例， 项目利用北京谱仪III所采集的高质量的J/ψ和ψ（2S）数据，针对轻介子衰变的开展了相关实验研究，并取得一系列创新研究成果。（1）首次发现etaprime-->rhopi。解决了二十年来来理论物理学家争论etaprime衰变重是否存在P波贡献的问题；(2) 首次确认etaprime-->gamma pi+pi- 衰变中含有其他成分（rho的激发态或box-anomaly)的贡献;(3)首次观测到a0(980)-f0(980)混合,对理解它们的内部结构提供了重要实验数据；（4）首次采用新方法精确测量etaprime的衰变分支比，并首次开展多个etarpime稀有衰变研究；（4）首次观测到X(2370)的新衰变模式和新矢量粒子X(1750）；（5）完成etarpime和omega达立兹图（Dalitz plot）分析。以上研究成果均发表在Phys. Rev. Lett., Phys. Rev. D 或 Eur. Phys. J. C 上。 . 这一系列研究成果不仅检验了低能区的理论模型，还丰富了轻介子谱的内容，为理解介子的内部结构提供了重要实验数据，受到广泛关注。上述结果多次被邀请在国际会议报告相关研究成果，并被邀请撰写综述文章。

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