BESIII实验上Omega重子激发态的寻找

Baryon state, which is a hadron state and composed of three quarks, is one of the hot topics in the particle and nuclear physics, especially the Omega baryon state composed of three strange quarks. However, There are few results from the study of the Omega baryon states. Only five Omega baryon states were discovered. Furthermore, only Omega(1672) has been determined to have spin-parity quantum number 3/2^+, while the spin-parity quantum number of the others have not been determined yet. Theorists proposed many models for explaining the quark component and nature of these Omega baryon states and predict the possible Omega baryons states. However, these models have not been approved or contradicted by the experimental results. Based on the BESIII data samples accumulated from 2009 to now, we will search for the excited Omega baryon states and determine their spin-parity quantum number. These experimental results are important for understanding the quark component and nature of the Omega baryon states, extending the Omega baryon spectrum and testing the different theoretical models.

重子是由三个夸克组成的强子，重子谱的研究一直是粒子物理与原子核物理研究的前沿热点之一，尤其是由三个奇异夸克组成的Omega重子态。实验上对Omega重子态的结果还很少，仅发现了五个Omega重子态。而且只有基态Omega(1672)的自旋宇称量子数被确定为3/2^+，其他四个Omega重子激发态的自旋宇称量子数至今都还没有被确定。理论上提出了很多模型来解释这些Omega重子态的夸克结构以及性质并预测可能存在的Omega重子态，然而至今还没有被实验所证实或反驳。基于北京谱仪III从2009年采集至今的数据，我们将开展对Omega激发态的寻找并测定其自旋宇称量子数。这些实验结果对理解Omega重子态的夸克结构和性质、丰富Omega重子谱以及检验不同理论模型的计算有重要意义。

实验上对Omega重子激发态的研究是近年来粒子物理实验研究的前沿热点之一，基于BESIII探测器获取的两个大样本psi(3686)和psi(3770)数据，包括27亿个psi(3686)事例和积分亮度为2.9 fb^-1的psi(3686)事例，本项目通过重建psi(3686)/psi(3770) -> Omega- anti-Omega^*+, anti-Omega^*+ -> gamma anti-Omega^+过程来寻找最轻的Omega重子激发态。利用部分重建技术重建衰变过程中的Omega-，并在Omega-的反冲质量谱上寻找anti-Omega^*+重子激发态。实验结果表明在1.7~2.1 GeV质量范围内不存在明显的Omega重子激发态。本项目也对质心能量在4.0~4.9 GeV区间的34个能量点总积分亮度为22.4 fb^-1的XYZ数据寻找可能存在的Omega重子激发态。同样利用部分重建技术重建e+e- -> Omega- anti-Omega^*+过程中的Omega，并在其反冲质量谱中寻找Omega重子激发态。实验结果也没有观察到明显的共振态结构。综上所述，本项目利用所有的BESIII数据寻找Omega重子激发态，虽然实验上没有发现明显的Omega重子激发态，但是这些实验结论也对理解Omega重子谱以及检验不同理论模型的计算提供了重要的实验依据。