北京谱仪III上e+e-→KKh_c和KK*η_c的实验研究

Charmonium states have been well described by the quark models. However, many newly discovered charmonium-like XYZ states show very exotic properties and they cannot be incorporated in the charmonium spectrum. There is growing evidence that at least some of these XYZ states are not conventional charmonia, theoretical models interpreting them as molecular states, multi-quark states, hybrids, or threshold effects have been proposed. However, there is no sufficient evidence to confirm or exclude any of these models. In this proposal, we will use large statistics data samples collected above 4.4 GeV at BESIII to study two new hadronic final states with a charmonium and light hadrons, e+e-→KKh_c and KK*η_c, search for new charmonium-like states with quantum numbers of 1-- in the e+e-→KKh_c and KK*η_c cross sections, and search for new charged charmonium-like Zcs (with c cbar u sbar) states in the Kh_c and K*η_c systems. These measurements will provide new experimental inputs to deepen our understanding of the existing charmonium-like states, test some theoretical models such as molecular states and threshold effects, broaden the horizon of hadronic structures, and promote the improvement and development of relevant theoretical models.

夸克模型很好地描述了粲偶素能谱，但是实验上发现的一系列类粲偶素XYZ粒子却不能被夸克模型所解释。越来越多的证据显示这些粒子并不是常规的粲偶素，理论上提出了如分子态、多夸克态、混杂态、阈效应等模型进行解释，但目前实验上还没有充分的证据证实或排除任何一种模型。本项目将利用BESIII实验在4.4GeV以上能量区间采集的大统计量数据，首次对强子衰变过程e+e-→KKh_c和KK*η_c进行测量和研究，进而在这两个过程的截面随能量点变化的曲线上寻找新的量子数为1--的类粲偶素，并且在Kh_c和K*η_c不变质量谱上寻找新的带电类粲偶素Zcs。这些测量都将为类粲偶素领域重要问题的解决提供新的实验输入，对分子态、阈效应等理论模型进行一定的检验。研究结果将加深对已知类粲偶素性质的理解，拓展对强子结构的认识，推动相关理论模型的完善和发展。

粲偶素能区的物理对于理解微扰和非微扰量子色动力学的性质、对探讨微扰-非微扰过渡区域强相互作用的行为非常重要，因此粲偶素物理的研究一直是高能物理领域的一个前沿热点问题。在本项基金的支持下，我们利用北京谱仪III采集的大统计量实验数据，研究e+e-→K+K-h_c过程，首次给出反应过程的截面测量结果，并且尝试在截面谱和Kh_c不变质量谱上寻找新的类粲偶素态。同时在本项基金的支持下，我们还测量e+e-→η'J/ψ、ωπ0和ωη等过程的截面谱分布，并在截面谱上对(类)粲偶素粒子进行寻找和研究；研究类粲偶素X(3872)和Z_c(4020)0的一些衰变模式，促进对于这些奇特态粒子性质的理解；并且寻找粲偶素ψ_2(3823)和h_c的一些新衰变道，其中首次发现ψ_2(3823)→γχ_c2存在的证据，首次测量h_c→π0J/ψ过程分支比的上限等。这些研究成果将有助于更好地理解粲偶素及类粲偶素的性质，为理论研究提供新的实验输入，推动相关理论模型的完善和发展。