BESIII实验上piDD*过程中Zc奇特强子共振参数及其产生截面的测量

In the year 2013, the BESIII experiment discovered several charged Zc exotic hadron states, which have generated a lot of interest in the scientific community. These new exotic states could be interpreted as molecule states, tetraquark states, etc. However, the current experimental results can not lead to a definite conclusion on the nature of these states. In this project, we will analyze the piDD* three-body final states process using the high luminosity data collected by high energy e+e- annihilation at the BESIII experiment. We will precisely measure the Zc resonance parameters (mass、width and angular distribution) and its production cross sections, and further investigate the structure and decay property of the Zc exotic state. In doing so, we try to reveal the relationship between the charged DD* structure Zc(3885)、charged Zc(3900)、neutral DD* structure and X(3872). We also determine the Zc production mechanism according to the lineshape of e+e- to pi Zc cross section, which provides important information for the QCD theory.

2013年北京谱仪III实验发现了几个带电Zc奇特强子态，在国际上引起广泛关注。这些新型强子态存在分子态、四夸克态等多种理论诠释，但目前的实验结果尚不足以得出确定的结论。本项目将利用BESIII实验上多个高能量点、高亮度正负电子对撞数据，通过piDD*三体粲介子末态过程，精确测量DD*上Zc奇特强子的共振参数(质量、宽度和角分布)及其产生截面；深入研究Zc粒子的结构和衰变性质，揭示DD*带电结构Zc(3885)、带电Zc(3900)、中性DD*结构、X(3872)等新型强子态之间的联系；利用DD*上奇特强子Zc产生截面随质心能量的变化关系确定Zc粒子的产生机制，为量子色动力学理论提供重要的信息。

利用北京谱仪III实验在4.26GeV和4.23GeV取得的积分亮度为826pb-1和1092pb-1正负电子对撞数据，精确测量了piDD*过程中带电和中性Zc奇特强子的质量、宽度等共振参数和产生截面。项目研究的最新结果显示：中性Zc奇特强子的质量和宽度与带电Zc奇特强子的质量和宽度在误差范围内一致，这确认了BESIII合作组对带电奇特强子的共振参数测量，高亮度的数据样本使得奇特强子的测量结果更加精确。在中性DD*中发现的共振结构Zc(3885)^0与X(3872)应该不是同一种基本粒子，因为两者的质量和宽度存在两倍以上的标准偏差。项目还利用北京谱仪III实验上收集的粲介子样本，精确测量了粲介子的半轻衰变分支比和强子衰变分支比，测量结果达到世界最高精度并被粒子数据手册收录。