北京谱仪III上的Zcs的寻找

Recently, many charmonium (bottomium)-like states are discovered by the experiments. These states, named XYZ, do not match to the expectations for any of the currently unassigned ccbar charmonium or bbar bottomonium states. Among these XYZ states, the charmonium-like state Zc(3900) was first discovered by the BESIII experiment. There are many theories to explain the nature of Zc(3900), however, it is still difficult to make a conclusion. One of the theory models believes that the near-threshold Zc(3900) is due to the influence of a nearby pole in the S-matrix, while another theory model predicts it is due to the Initial Single Pion Emission (ISPE) mechanism. Furthermore, as a nature extension, these two models both predict the existence of the Zcs, which is the strange partner of Zc(3900) and is consist of ccbar qsbar or ccbar sqbar (q denotes u or d quark). In this application, we propose to study the KKJpsi, KDsDbar, KDsD*0 and KDs*D0 channels. We measure their Born cross sections and search for the Zcs in the K-recoiling system using the BESIII data. We expect to find the Zcs or obtain the upper limit of the Zcs yields. With these information, we would achieve a better understanding of the nature of the Zc(3900), and even a better understanding of the QCD theory.

XYZ粒子是传统量子色动力学理论预期之外的强子态，理解它们的产生和衰变机制是目前高能粒子物理领域的前沿热点问题。其中，Zc(3900)是在北京谱议III上发现的类粲偶素态，对其结构的解释目前尚无定论。有理论模型认为Zc(3900)是在DD*阈附近受S矩阵极点影响的运动学效应，也有理论认为其是初态单pi介子发射机制（ISPE）的产物。不仅如此，这两种理论模型还预言了新强子态Zcs的存在。Zcs是Zc(3900)的奇异伴随态，其夸克组成为ccbar u(d)sbar。本项目拟利用北京谱仪III获取的数据，测量KKJpsi、 KDsDbar、 KDsD*0 和KDs*D0四个过程的玻恩截面,并在K介子的反冲侧寻找Zcs。研究结果预期找到Zcs，或得到Zcs的产额上限。本研究可以验证预言Zcs的理论模型的正确性，更好地理解Zc(3900)的产生和衰变机制，从而促进量子色动力学相关理论的完善和发展。

奇特强子态的寻找是高能物理实验领域的热点问题。Zcs粒子作为Zc粒子的奇异伴随态，被多种理论模型所预言。.本项目利用BESIII实验质心系能量大于4GeV的数据，尝试在e+e-->KKη_c末态的Kη_c组合中寻找Zcs。该研究通过η_c的16个衰变道，对η_c进行重建。研究内容包括：各衰变道的事例选择、本底分析、KKη_c玻恩截面的测量、K反冲不变质量谱的分析、误差分析等内容。相关研究方法已经完成，并完成了e+e-->KKη_c过程90%置信区间上限的测量。.另外，利用BESIII实验质心系能量大于4.6GeV的部分数据，本项目对e+e-->KDsD*/KDs*D过程进行了独立检查。完成了包括事例选择、本底分析、K反冲不变质量谱的分析、KDsD*/KDs*D两过程比例测量的研究内容。该结果与合作组成员的结果一致。.上述两个过程的研究，e+e-->KKη_c过程未发现显著Zcs的信号，e+e-->KDsD*/KDs*D发现了Zcs的可能候选。该结果提供了实验上关于Zcs的关键实验信息，有助于理解Zc/Zcs的组成以及量子色动力学的机制。