Strange Form Factors and a Low Energy Standard Model Test

这笔拨款支持寻求关于物质的两个基本问题的答案的研究。第一个问题是，核子中奇怪的夸克-反夸克对的海洋在确定其电磁性质方面扮演了什么角色？我们正在参加托马斯·杰斐逊国家加速器设施的G0实验，以解决这个问题。这项实验测量了在大范围的动量转移中，极化电子从质子和氘中散射时违反宇称的不对称性；这将允许分别提取奇怪的电和磁形状因子。这项实验将在这一赠款期间处于数据采集和分析阶段。第二个问题是，在弱电物理的标准模型之外，是否还有任何新的物理。这个问题将由TJNAF的量子弱实验来解决，该实验将在极低的动量转移下通过破坏宇称的电子散射来测量质子的中性弱电荷。质子的弱电荷在标准模型中有一个明确的预测；对它的精确测量对扩展标准模型的许多常见情况很敏感。在这笔赠款期间，这项实验将处于建设和早期数据采集阶段。我们团队将为量子弱实验设计和建造三个硬件-一组漂移室，一个光度监测器，和一个微型环磁铁。这些项目涉及许多硬件和软件任务，这些任务将有助于博士后研究员以及从事该项目的研究生和本科生的教育。

This grant supports research that seeks the answer to two fundamental questions about matter. The first is what role does the sea of strange quark-antiquark pairs in the nucleon play in the determination of its electromagnetic properties? We are participating in the G0 experiment at Thomas Jefferson National Accelerator Facility to address this issue. The experiment measures the parity-violating asymmetry in the scattering of polarized electrons from the proton and deuteron over a wide range of momentum transfers; this will allow for the strange electric and magnetic form factors to be separately extracted. This experiment will be in a data-taking and analysis phase during this grant period. The second question is whether or not there is any new physics beyond the Standard Model of electroweak physics. This question will be addressed by the Qweak experiment at TJNAF, which will measure the proton's neutral weak charge via parity-violating electon scattering at very low momentum transfer. The proton's weak charge has a well-defined prediction in the Standard Model; a precise measurement of it is sensitive to many poplular scenarios for extending the Standard Model. This experiment will be in a construction and early data-taking phase during the period of this grant. Our group will design and construct three pieces of hardware for the Qweak experiment - a set of drift chambers, a luminosity monitor, and a mini-torus magnet. These projects involve many hardware and software tasks that will contribute to the education of a postdoctoral fellow and graduate and undergraduate students working on the project.