在重夸克偶素的辐射衰变中寻找胶球存在的迹象

Since the Quantum Chromodynamics is founded，glueball is one of particles which are predicted in theory but not found in experiment. In recently years, some exotic states such as tetraquark are found in experiment, so people hope to get a break in glueball searching. At present, theorists and experimenters tend to believe that glueball may not exist independently, but to be observed as on mass-shell physical meson through mixing with meson composed of quark anti-quark pair and/or multi-quark states with the same quantum numbers. Therefore making sure those mesons whether contains glueball or not and how many percentage of them is the key to verify the basic theory of quantum chromodynamics. This is also the basic target of our project..The present project is intended to searching the hint of glueball in radiative decays of heavy quarkonium based on the previous research and some theoretical prediction about glueball such as the Lattice. The project contents are：searching the hint of glueball in the final state product in the radiative decays of bottomonium to charmonium and charmonium-like states, the electromagnetic transition of charmonium and the radiative decays of charmonium to light hadrons. These researches can both provide theoretical enlightenment for glueball exploring and promote accurate measurement of several bottomonium decay channels in Belle and LHCb.

自从量子色动力学创建以来，胶球就是理论上预言存在，但是实验上尚未找到的粒子之一。近些年来，实验上不断发现四夸克态等新奇特态，人们希望在胶球寻找方面取得一些突破。目前，理论家和实验家有明确的倾向：胶球也许不能独立存在，而是与其他量子数相同的正反夸克对构成的介子，甚至多夸克态混合，成为在质量壳上的可观测物理介子，因而确定这些介子中是否含有胶球成分，比例是多少就成为验证量子色动力学基本理论的关键，这也是本课题的主要目标。.本项目计划在以往研究的基础上，结合格点计算等理论对胶球的预言，在重夸克偶素的辐射衰变中寻找胶球存在的迹象。主要研究内容有：在底偶素到粲偶素和类粲偶素的辐射衰变过程、粲偶素的电磁跃迁中，以及粲偶素到轻强子的辐射衰变过程中研究末态产物胶球存在的迹象。这些研究既可以为将来胶球的探测提供理论启示，还可以促使Belle和LHCb实验组对底偶素的多个衰变道进行精确的测量。

胶球是量子色动力学预言的，实验上尚未找到的粒子之一。寻找这种粒子，有助于我们更好的理解轻夸克与胶子以及胶子之间的非微扰相互作用。标量胶球作为可能能量最低态的胶球，备受关注。本项目在对标量胶球研究的众多基础之上，研究了标量介子f0族谱中可能混有的胶球成分。经过计算，发现f0(1710)的主要成分为胶球。同时还计算了f0(1370)、f0(1500)和f0(1710)这三个物理态到轻介子对以及双光子的分支比的比值，以期望被未来的实验所验证。另外，我们还研究了标量新物理粒子可能对18.4GeV和6.9GeV能标附近共振峰的贡献。考虑到实验限制条件后，在不考虑具体模型的情况下，新物理标量粒子很难解释18.4GeV能标附近的共振峰现象，但是可以解释6.9GeV能标附近共振峰现象。