璨重子谱的相对论手征夸克模型研究

The spectrums and structures of the heavy-flavored baryons including the excited states has long been one of the hot topics in the frontier field of strong interaction and hadron physics, and become an important and ideal place to test the theory of strong interaction, Quantum Chromodynamics(QCD). By incoporating phenomenological potentials and interactions inspired by QCD, the quark models become an important and flexible theoretical tools to study the spectrums and structures of hadrons, and has recently been extended to the versions of being relativistic and of many-body nature. This project plans to study the spectrums and quark structures of the charmed baryons including excited states via the relativistic chiral quark model nonlinearly realized, and to determine the quantum numbers of the partially observed charmed baryons(Lamda_c and Sigma_c),thereby clarifying the role of QCD symmetries and quark interactions in hadron structure. This will be done by introducing the chiral field coupling nonlinearly realized and the many-body field-theoretical methods,and solving the baryon wavefunctions in the approximations of the self-consistent mean-field and the heavy-quark limits, with the help of variational Monte-Carlo methods and so on, so as to compute spectrums of these charmed baryons as well as the related effects of strong decay widths, and to determine the corresponding quantum numbers.

包括激发态的重味重子谱和结构问题的研究，一直是强相互作用和强子物理前沿研究领域的热点问题之一，同时成为检验强相互作用量子色动力学(QCD)的一个重要的理想场所。夸克模型通过引入具有QCD精神的唯象势和唯象相互作用，成为研究强子谱和强子结构的一个重要而灵活的理论工具，并在近年来向着相对论情形及多体场论情形推广，以便使模型更靠近QCD。本课题拟利用非线性实现的相对论手征夸克模型研究包括激发态在内的璨重子谱及其夸克结构，确定部分实验观测到的璨重子（Λc和Σc）的量子数，由此阐明QCD对称性和夸克相互作用在强子结构中所扮演的角色。主要通过在相对论性的手征夸克模型中引入非线性实现的手征场耦合和多体场论技术，在手征场的自洽平均场近似和重夸克近似下，利用变分蒙特卡洛模拟等技术求解重子波函数，并计算璨重子Λc和Σc的谱结构和强衰变宽度效应，确定相应的量子数。

本课题通过求解相对论夸克模型研究了强相互作用领域的前沿热点问题之一：基态和激发态重子谱和重味介子的辐射衰变。首先，利用QCD泛函研究了Dirac型相对论夸克模型，证明了组份质量来自夸克标量凝聚；基于手征夸克模型研究了重子共振态的Diakonov大Nc平均场集体激发理论及其重子共振态谱公式参数的数值优化。其次，项目详细研究并数值地求解了大Nc-相对论手征夸克模型,计算了重子八重态和十重态强作用超精细质量分裂和同位旋质量劈裂，获得与核子2014数据表相符的核子质量谱；利用超精细质量劈裂首次预言了’t Hooft耦合常数对轻味重子约为1.57，对于粲味重子是1.64，对轻味介子是1.89 。最后，我们系统地研究了Godfrey-Isgur相对论夸克模型框架下的底奇异介子的辐射衰变，给出了底奇异介子E1和M1辐射衰变分宽度，为实验上寻找底奇异介子提供了理论依据。