Precision Studies of the Standard Model using Parity-Violating Electron Scattering

为了理解物质的基本结构，大多数物理学家采取了还原主义的方法，将物质分解为基本成分：电子、夸克、胶子等。除了这些构成粒子物理学标准模型（我们目前关于物质基本粒子及其相互作用的最佳理论）的已知基本粒子之外，可能还存在更多尚未发现的基本粒子。该项目支持在托马斯·杰斐逊国家加速器设施（杰斐逊实验室）的两个大型实验中精确测量质子和电子的所谓电弱特性。这些测量结果与标准模型预测之间的差异将指向标准模型中尚未包含的新物理过程。在达成协议的情况下，将排除对标准模型的某些扩展。精确的电弱测量为在低能电子加速器上测试粒子物理标准模型提供了一种独特的方法。杰弗逊实验室是目前世界领先的违反奇偶电子散射实验实验室，非常适合完成雄心勃勃的Qweak和MOLLER实验。这两个实验的结果，特别是结合欧洲核子研究中心大型强子对撞机的结果，将使我们能够约束超出标准模型的物理模型。Qweak实验于2010年5月开始，收集数据至2012年5月。该实验仅利用5%的可用数据就首次确定了质子的弱电荷，并旨在利用完整的数据集对标准模型之外的物理进行精确测量。研究人员将继续在轨道重建、数据分析和模拟工作中发挥核心作用，这对成功完成实验至关重要。MOLLER实验预计最早将于2017年运行，并将测量电弱混合角，其精度可与通过测量电子的弱电荷进行的最佳高能测量相媲美。研究人员将在MOLLER实验的轨道重建探测器的开发以及基于极化原子氢气中的MOLLER散射的新型电子束偏振计的开发中发挥主导作用。这种新的极化计将允许测量电子极化达到0.4%的要求精度，这种技术也将适用于其他电子加速器。研究人员正在努力通过威廉玛丽REU项目的具体招募工作来增加物理学领域的经济和种族多样性。研究人员致力于增加物理系与更广泛的社区之间的互动，通过组织“物理测试”，这是物理系每年的开放日，以及通过“星期六上午物理”，这是一个针对当地中学生和高中生的定期公共宣传讲座系列。

In the quest to understand the fundamental structure of matter, most physicists have taken a reductionist approach by breaking down matter into its elementary constituents: electrons, quarks, gluons, etc. In addition to these known elementary particles that constitute the Standard Model of particle physics (our current best theory of the fundamental particles of matter and their interactions), there may exist more as-of-yet undiscovered elementary particles.This project supports efforts to precisely measure so-called electroweak properties of the proton and of the electron in two large experiments at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). Discrepancies between these measurements and the predictions of the Standard Model will point to new physical processes that are not yet included in the Standard Model. In case of agreement certain extensions to the Standard Model will be ruled out.Precision electroweak measurements present a unique approach to test the Standard Model of particle physics at low-energy electron accelerators. Jefferson Lab is currently the world's leading laboratory for these parity-violating electron scattering experiments, and is uniquely suited to complete the ambitious Qweak and MOLLER experiments. The results of both experiments, by themselves but especially in combination with the results from the Large Hadron Collider at CERN, will allow us to constrain models of physics beyond the Standard Model.The Qweak experiment started in May 2010 and collected data until May 2012. The experiment has performed the first determination of the weak charge of the proton with only 5% of the available data, and is aiming to make a precision measurement sensitive to physics beyond the Standard Model with the full data set. The investigators will continue their central role in the track reconstruction, data analysis, and simulation efforts crucial to the successful completion of the experiment. The MOLLER experiment is expected to run as early as 2017, and will measure the electroweak mixing angle to a precision comparable to the best available high-energy measurements through a measurement of the weak charge of the electron. The investigators will take a leading role in the development of the track reconstruction detectors for the MOLLER experiment, and the development of a novel type of electron beam polarimeter based on Moller scattering in polarized atomic hydrogen gas. This new polarimeter will allow the measurement of the electron polarization to the required precision of 0.4% using a technique that will be applicable at other electron accelerators as well.The investigators are working to increase economic and racial diversity in physics through specific recruiting efforts for the William & Mary REU program. The investigators are committed to increasing interaction between the physics department and the broader community through the organization of "PhysicsFest," a yearly physics department open house, and through "Saturday Morning Physics," a regular public outreach lecture series aimed at local middle and high school students.