The hadron spectrum from QCD sum-rules

粒子物理学是在已知的最小距离尺度上研究物质和力的学科。当我们移动到越来越小的距离时，出现了一个特定的层次：物质由分子组成，分子由原子组成，原子由电子和原子核组成，原子核由质子和中子组成。20世纪70年代的S认识到，质子和中子本身是由更小的称为夸克的粒子组成的。负责将夸克聚集在一起的力被称为强核力，相应的物理理论被称为量子色动力学(QCD)。除了质子和中子之外的夸克组合也是可能的，由此产生的束缚态统称为强子。粒子物理学目前正在研究的一个重要问题是，试图根据每个强子所包含的夸克的已知性质来预测这些强子的性质。这些特性包括质量、寿命和衰变模式。具体地说，我正在研究一类尚未被发现的粒子，称为杂化粒子，理论上预测了它的存在。然而，这种粒子尚未在实验中得到最终鉴定。

Particle physics is the study of matter and forces at the smallest known distance scales. As we move to smaller and smaller distances, a certain hierarchy emerges: matter is made of molecules, molecules are made of atoms, atoms are made of electrons and nuclei, and nuclei are made of protons and neutrons. It was realized in the 1970's that protons and neutrons themselves are made of even smaller particles called quarks. The force responsible for holding the quarks together is called the strong nuclear force and the corresponding physical theory is called quantum chromodynamics (QCD). Quark combinations aside from protons and neutrons are also possible, and the resulting bound states are collectively referred to as hadrons. An important problem currently being researched in particle physics is that of trying to predict the properties of these hadrons based on known properties of the quarks that each contains. Such properties include mass, lifetime, and decay modes. In particular, I am investigating an as yet undiscovered class of particles called hybrids whose existence is predicted by theory. However, such particles have yet to be conclusively identified in experiment.