大科学装置上轻味重子激发态的理论研究

Based on the importance of baryons to the understanding of the non-perturbative strong interactions, and the experimental programs of baryons are being or to be carried out at many large scientific facilities, we will study some scattering and decay processes related to these experiments with a constituent quark model (CQM). From these processes we will extract the properties of baryon resonances and look for the missing resonances. Specifically, we expect to obtain the following innovative results: (1) The CQM will be first extended to study the γp→KΛ(1405, 1520), KΣ(1385) processes. To deal with these reactions, we will develop new partial wave analysis (PWA) methods. In these reactions, we will looking for new nucleon resonances with a mass around 2.0 GeV. (2) The CQM will be first extended to study the πp→nγ and Kp→Λγ/Σγ processes. After a PWA being carried out, from these processes we can understand the properties of strong and electromagnetic decays of baryon resonances, especially for N(1440) and Λ(1405), and clarify some puzzles about them. (3) With the CQM we will carry out a combined study of the seven KN reactions Kp→Kp/Σπ/Λπ/Kn/ηΛ, where we will extract information of Λ and Σ resonances, and finally establish a more abundant spectrum. (4) With the CQM, we will study the strong/electromagnetic decays of baryons, and further discuss the observations of the missing states by using these decays. We hope our study can provide some useful references to observe the missing states in forthcoming experiments.

基于重子对理解非微扰强相互作用的重要性，以及各大科学装置正开展的或拟开展的重子研究计划，我们拟用夸克模型从夸克层次研究强子散射和衰变过程，在过程中探索轻味重子激发态的性质，寻找丢失的共振态。拟在如下方面取得创新成果：(1) 首次在夸克层面研究γp→ KΛ (1405,1520), KΣ(1385)过程，发展新的分波分析方法，在过程中寻找质量约2.0 GeV的新重子激发态；(2) 首次在夸克层面研究πp→nγ和Kp→Λγ/Σγ，在过程中理解重子共振态，特别是N(1440)和Λ(1405)，的电磁和强衰变性质，为澄清一些长期的疑惑提供线索；(3) 在夸克模型框架下系统完成7个KN散射过程Kp→Kp/Σπ/Λπ/Kn/ηΛ的联合分析，提取Λ和Σ超子共振态的信息，发展和完善超子谱；(4) 在夸克模型框架下研究Ξ和Ω激发态的强衰变和辐射衰变,据此提出观测策略, 为实验寻找丢失共振态提供参考。

项目瞄准国际上各大科学装置正开展的或拟开展的强子谱研究计划，利用夸克模型对重子、介子以及四夸克态的质量谱和衰变性质开展了系统的研究，取得了系列创新成果。具体如下：（1）在重子谱方面，系统地研究了三夸克系统sss，ccc，bbb的质量谱和强/电磁衰变性质，率先从传统三夸克态的角度解释了Ω(2012)的性质，得到了后续实验的支持，系列成果为未来实验寻找更多新态提供理论参考。同时也系统分析了λ型P波和D波单重味重子的强衰变/电磁衰变性质，对新发现的重味重子态的结构提出理论解释同时为实验寻找建议了可能途径，部分预言得到实验证实。（2）在介子谱方面，系统研究计算了ϕ介子质量谱和轻-重介子Bc,D/Ds, B/Bs质量谱，并进一步研究了它们的强衰变/电磁衰变性质，对实验上发现的态的夸克模型分类给出了合理解释，为实验寻找建议了可能途径。（3）在四夸克态方面，系统研究计算了全粲、全奇异、全底四夸克态质量谱，首次给出了1D波以内的完整的质量谱，对LHCb新发现的X(6900)等可能四夸克给出了理论解释，系列成果为未来实验寻找提供重要理论参考。