XYZ 粒子质量谱及衰变性质研究

Recently, more and more new hadronic states have been found in high energy experiments. These states, named XYZ particles, have properties, such as mass spectra, decay widths, et al, which cannot be explained by usual quark models. This project tries to study the properties of these particles by using a new method. Two aspects will be considered. First, the mass of particles which are near thresholds is affected by the coupled-channel effects. Usually, this is studied by non-relativistic models. Here, by using Bethe-Salpeter equation, we try to construct a relativistic coupled-channel model, then get more reasonable mass and corresponding wave functions. Second, we will use results of the former step to study the main decay channels of these particles. For the OZI-allowed strong decay, the non-relativistic method will be improved and extended. Also, the microscopic mechanism of decays will be investigated. For the OZI-forbidden ones, electromagnetic decays could be very important. Here we mainly study one-photon and three-photon transitions. The studies above will be helpful to further confirmation of the inner structure for new hedonic states, and supply more theoretical basis to future experiments.

最近，高能粒子实验中发现了许多新的强子态。其性质，如质量谱、衰变宽度等，并不能被以往的夸克模型所解释，被称为 XYZ 粒子。本课题试图通过新的研究方法对这些粒子的性质进行研究。主要包括两个方面。首先，在阈值附近的粒子，其质量要受到所谓的耦合道效应的影响。以往所采用的模型都是非相对论的。这里通过将 Bethe-Salpeter 方程同非相对论情形的耦合道模型相结合，试图对其进行相对论性扩展，进而得到更为合理的质量谱及相应波函数；其次，将采用前一步得到的结果来研究这些粒子的主要衰变道。对于 OZI 允许的强衰变，将对通常的非相对论方法进行完善及扩展，并试图对衰变的微观机制进行探讨。对于 OZI 禁戒的过程，电磁衰变将变得非常重要。这里将主要讨论粒子的单光子及三光子跃迁过程。上述研究将有助于对新发现强子态的内部结构进一步确认，并为实验上对其进行更加深入的研究提供理论依据。