Electromagnetic Probes of Hadronic Matter

这一NSF奖支持我们在杰斐逊实验室使用电磁探测器在基本水平上研究强子物质的持续研究计划。我们的团队专注于四项实验工作，以测试夸克胶子水平上粒子相互作用的基本性质。ISU目前正在建造五个粒子跟踪漂移室，以支持杰斐逊实验室的B12GeV大厅计划。我们的一项实验从质子和重离子上的线偏振光子的介子光产生中提取了偏振能观，并将在这一资助期间产生两篇ISU博士论文。另一项实验将研究夸克在极端运动学中的分布，在极端运动学中，夸克携带着核子的大部分动量。杰斐逊实验室B厅正在进行一项对介子寿命的高精度测量。这项实验工作旨在探索中性带电介子衰变成两个光子的机制，以严格测试限制尺度的量子色动力学。在A厅的另一个高精度实验，Moller，利用弱相互作用的宇称违反性质，测量标准模型的基本参数，即Weinberg(或混合)角，使其相对不确定度为0.1%。当与其他实验相结合时，这一测量将对我们目前版本的标准模型的拟议扩展施加强烈的限制。JLab的这些研究计划、ISU的加速器设施以及该集团探测器科学实验室的连续探测器建设项目，结合在一起，为四名研究生提供了广泛的经验，并培养了下一代科学家。

This NSF award supports our continuing research program at Jefferson Lab using electromagnetic probes to study hadronic matter at the fundamental level. Our group focuses on four experimental efforts that test the basic nature of particle interactions at the quark gluon level. Five particle tracking drift chambers are currently being constructed at ISU to support Jefferson Lab's Hall B 12 GeV program. One of our experiments extracts polarization observables from meson photoproduction with linearly-polarized photons on the proton and deuteron and will result in two ISU PhD theses during this funding period. Another experiment will investigate quark distributions at extreme kinematics where the quarks carry most of the nucleon's momentum. A high-precision measurement of the pion lifetime is being undertaken in Jefferson Lab's Hall B. This experimental effort seeks to probe the mechanism through which a neutral charged pion can decay into two photons to stringently test confinement-scale quantum chromodynamics. Another high-precision experiment in Hall A, MOLLER, uses the parity-violating property of the weak interaction to measure a fundamental parameter of the Standard Model known as the Weinberg (or mixing) angle to within a relative uncertainty of 0.1%. When combined with other experiments, this measurement will place strong constraints on proposed extensions to our present version of the Standard Model. These research programs at JLab, the accelerator facilities at ISU, and continuous detector construction projects in the group's Laboratory for Detector Science, combine in an active program to provide a breadth of experiences for four graduate students and to train the next generation of scientists.