BESIII上双奇异重子极化的研究

根据粒子物理标准模型可知，人们所熟知的普通物质都是由自旋为1/2的费米子构成。然而我们自认为很清楚的这些普通物质的表现也给人们带来了一个难解之谜，那就是宇宙中正反物质不对称的问题。迄今为止，人们还不清楚该问题的本质。有理论指出重子数产生机制会解开正反物质不对称之谜，但是要理解此理论需要三个条件，即重子数破坏、CP破坏和脱离热平衡，然而由于实验信息的匮乏，目前我们还不能很好的理解这些重子数产生条件。尽管目前一些粒子物理实验组在K介子、B介子、D介子的弱衰变中观测到了CP破坏的证据，但是这些结果仍然不足以解释自然界中所有的正反物质不对称。尤其在重子弱衰变方面，对CP破坏的研究少之又少。因此，为了进一步理解正反物质不对称问题。本项目将利用BESIII实验采集的100亿的J/psi数据样本，对Ξ0、Ξ-、Ξ(1530)0、Ξ(1530)-等双奇异重子的极化进行研究，测量其反对称衰变参数和CP破坏。

According to the standard model of particle physics, we know that ordinary matter is composed of fermions with a spin of 1/2. However, even if we think it is very clear that the performance of these ordinary matter also brings us a mystery, i.e. the matter-antimatter asymmetry problem in the universe. So far, the nature of the matter-antimatter asymmetry has not been understood. It has been pointed out that the baryogenesis mechanism will take some answers for this mystery. To understand the baryogenesis mechanism, we need three conditions: baryon number violation, CP violation and thermal equilibrium violation. So far, we have not understood well for these conditions due to the shortage of experimental information. Although some particle physics experimental groups have observed the CP violation in the weak decays of K meson, B meson and D meson, these results are still not enough to explain all the matter-antimatter asymmetries in nature. Especially in the weak decay of baryons, there are few researches on CP. Therefore, to further understand the matter-antimatter asymmetry problem. This project will perform a study of the polarization for doubly-strange baryon, such as Ξ^0, Ξ^-, Ξ(1530)^0, Ξ(1530)^-, and measure their antisymmetric decay parameters and CP violation, using 10 billion data samples collected at the J /psi energy region with BESIII experiment.