Study of Hadronic Structure Using Electromagnetic Probes

这项研究是由俄亥俄大学物理与天文系的丹尼尔·卡门教授和肯尼斯·希克斯教授在核物理和粒子物理的交叉领域进行的。其中一个目标是研究亚原子粒子的产生，这些粒子的组成中至少有一个“奇怪”的夸克。奇异夸克比构成原子核中常见粒子（如质子和中子）的传统“上”夸克或“下”夸克重。有趣的是，涉及具有“奇异性”的粒子的研究代表了研究由非奇异夸克组成的物质的动力学和结构的新方法。这是通过理解没有奇异性的粒子如何衰变成含有奇异夸克的粒子来实现的。这些实验研究为粒子的夸克结构及其激发态的基本理论提供了更多的信息和约束，即量子色动力学（QCD）。已知亚原子粒子集的一个可能扩展是发现“外来”粒子，这些粒子是QCD规则允许的，但尚未在实验中看到。特别是，结合夸克的胶本身可以携带粒子自旋量子数的一部分，而这些粒子被预测是存在的。了解这种胶的性质是核物理学领域最重要的未解问题之一。卡曼和希克斯在弗吉尼亚州纽波特纽斯的托马斯·杰斐逊国家加速器设施（杰斐逊实验室）进行研究，他们正在寻找奇异粒子的迹象，如果找到的话，将扩展我们对将夸克结合成亚原子粒子和我们周围物质结构的强作用力的认识。

The research being done by Professors Daniel Carman and Kenneth Hicks of the Department of Physics and Astronomy at Ohio University is conducted in the area of intersection between nuclear and particle physics. One goal is to study the production of subatomic particles having at least one "strange" quark in their makeup. The strange quark is heavier than the conventional "up" or "down" quarks that make up common particles found in the nucleus, like the proton and the neutron. Interestingly, studies involving particles with "strangeness" represent a new way to investigate the dynamics and structure of matter composed of non-strange quarks. Thisis accomplished by understanding how particles without strangeness decay intoparticles containing these strange quarks. These experimental studies provide more information and constraints for the underlying theory of the quark structure of particles and their excited states known as quantum chromodynamics (QCD). One possible extension to the known set of subatomic particles would be the discovery of "exotic" particles which are allowed by the rules of QCD, but not yet seen experimentally. In particular, the glue which binds quarks can itself carry a portion of the spin quantum numbers of a particle, and these particles are predicted to exist. Understanding the nature of this glue is one of the mostimportant unanswered question in the field of nuclear physics. Experiments at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Newport News, VA, where Carman and Hicks do their research, are searching for signs of exotic particles, which (if found) will extend our knowledge of the strong force that binds quarks together into subatomic particles and into the very structure of the matter around us.