Search for glueballs in charmonia decays

胶子的相互作用是强相互作用量子色动力学（QCD）理论的核心部分。胶子的自相互作用应该导致只包含胶子作为成分的状态的存在，胶球。从理论的角度来看，它们具有良好的动机，例如，晶格计算预测了具有不同量子数和质量的整个谱。在实验上，要确定胶球共振的光谱观察要困难得多。这是由于强子共振通常在宽度上重叠并相互混合，使得胶球的分配模糊不清。这种情况可以通过观察被认为主要涉及胶子的反应中的共振而得到改善。粲子衰变为轻夸克就属于这一类。在这里观察到的新共振和在双光子过程（见TP Heinsius）等缺乏胶子的反应中未观察到的共振将是共振胶子特征的强烈暗示。BESIII的高统计数据允许对胶球衰变进行详细的研究，调查它们似乎是目前唯一有希望取得进展的实验方法。这样，处理迄今为止推测的胶球结构或描述介子通过中间胶子状态进行强子化的理论就可以得到检验和改进。为了在始终存在的强子背景中清楚地分类未知共振，需要进行详细的部分波分析。要取得最好的成果，就需要Forschergruppe内部的密切合作。

The interaction of gluons is a central part of the accepted theory of the strong interaction Quantum Chromo Dynamics (QCD). The self interaction of gluons should lead to the existence of states containing only gluons as constituents, glueballs. From a theoretical point-of-view they are well motivated and e.g. lattice calculations predict a whole spectrum of them with different quantum numbers and masses. Experimentally it is much more difficult to pin down the spectroscopic observation of a resonance as glueball. This is owed to the fact that hadronic resonances often overlap in their widths and mix with each other making the assignment as glueball ambiguous. The situation can be improved by observing resonances in reactions believed to involve mainly gluons. The decay of charmonia into light quarks belongs to this class. The observation of new resonances here and the non-observation in gluon-poor reactions like two-photon processes (see TP Heinsius) would be a strong hint for the gluonic character of the resonance. The high-statistics data from BESIII then allow for a detailed study of glueball decays and investigating them seems currently the only experimental way promising progress. This way, theories dealing with the so far speculative structure of glueballs or describing the hadronization of mesons proceeding via intermediate gluon states could be checked and refined. In order to clearly classify unknown resonances among the always present hadronic background a detailed partial-wave analysis is required. The achievements of the best possible results asks for a close collaboration within the Forschergruppe.