Precision Electroweak Measurements using Parity-Violating Polarized Electron Scattering

使用违反奇偶校验的偏振电子散射进行精密电弱测量

• 批准号: 1206053
• 负责人: Wouter Deconinck
• 金额: $ 30万
• 依托单位: College of William and Mary
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206053&HistoricalAwards=false
• 关键词: Precision; Electroweak; Measurements; using; Parity

This grant supports efforts to measure to a very high precision a fundamental property of the proton and the electron. By comparing our measurements with predicted values we can test the Standard Model of particle physics, our current best theory of fundamental particles and their interactions. Deviations from the predictions will point to new physical processes that are not included in the Standard Model. The Thomas Jefferson National Accelerator Facility, or Jefferson Lab, is the world's leading laboratory for parity-violating electron scattering experiments. In two large collaborative experiments at Jefferson Lab, we will measure the 'weak' charge of the proton and the electron by scattering energetic electrons off a liquid hydrogen target. The weak charge is a property analogous to the well-known electric charge, but mediated by the weak force that is responsible for some radioactive decays. The Qweak experiment started in May 2010 and will collect data until May 2012. This experiment will measure for the first time the weak charge of the proton. Our group will use the new Compton polarimeter to measure the electron beam polarization, and we will develop the track reconstruction software for the determination of the reaction kinematics. The MOLLER experiment is expected to run after 2014, and will measure the weak charge of the electron. Our group is taking a leading role in the development of a novel type of electron beam polarimeter based on electron-electron scattering in polarized atomic hydrogen gas. This will allow for the measurement of the electron beam polarization to the required precision. This new polarimeter will demonstrate technology that can be applied at other accelerators.In the quest to understand the fundamental structure of matter, most physicists have taken a reductionist approach by breaking matter down to its elementary constituents: electrons, quarks, gluons, etc. In addition to the known elementary particles that constitute the Standard Model of particle physics, there may exist as-of-yet-undiscovered heavier elementary particles. At the energy frontier, ever more powerful accelerators (such as the Large Hadron Collider) aim to create those heavy particles directly. In contrast, at the intensity frontier we make very precise measurements at moderate energy scales. Jefferson Lab is at the forefront of precision measurements using the technique of parity-violating electron scattering, which exploits the small differences between reactions and their mirror image. The development of accelerators, particle detectors, and data analysis techniques has found many applications in industry, from radiation treatment for cancer and medical imaging to financial analysis. At the College of William & Mary, a PhD-granting liberal arts university within 30 minutes of Jefferson Lab, we present our graduate students with excellent career prospects, and we actively involve undergraduate students in the frontiers of research and train them to become the next generation of innovators.

这笔赠款支持以非常高的精度测量质子和电子的基本性质的努力。通过将我们的测量值与预测值进行比较，我们可以测试粒子物理的标准模型，这是我们目前关于基本粒子及其相互作用的最好理论。与预测的偏差将指向标准模型中没有包括的新物理过程。托马斯·杰斐逊国家加速器设施，或称杰斐逊实验室，是世界领先的违反宇称的电子散射实验实验室。在杰斐逊实验室的两个大型合作实验中，我们将通过将高能电子从液氢目标上散射来测量质子和电子的“弱”电荷。弱电荷是一种类似于众所周知的电荷的性质，但受到导致某些放射性衰变的弱力的调节。QWeek实验于2010年5月开始，收集数据将持续到2012年5月。这项实验将首次测量质子的弱电荷。我们小组将使用新的康普顿偏振仪来测量电子束的极化，并将开发用于确定反应运动学的轨迹重建软件。穆勒实验预计将在2014年后运行，并将测量电子的微弱电荷。我们团队在开发一种新型的电子束偏振仪方面发挥了主导作用，这种偏振仪基于极化原子氢气中的电子-电子散射。这将使电子束极化测量达到所需的精度。这种新的旋光仪将展示可以应用于其他加速器的技术。在寻求了解物质的基本结构的过程中，大多数物理学家采取了一种简化论的方法，将物质分解为其基本成分：电子、夸克、胶子等。除了构成粒子物理标准模型的已知基本粒子外，可能存在尚未被发现的更重的基本粒子。在能源前沿，更强大的加速器(如大型强子对撞机)旨在直接创造这些重粒子。相比之下，在强度边界，我们在中等能量尺度下进行非常精确的测量。杰斐逊实验室在使用破坏宇称的电子散射技术进行精确测量方面走在了前列，该技术利用了反应和它们的镜像之间的微小差异。加速器、粒子探测器和数据分析技术的发展在工业上得到了许多应用，从癌症的放射治疗到医学成像到金融分析。威廉与玛丽学院是一所授予博士学位的文科大学，距离杰斐逊实验室只有30分钟的路程。我们为研究生展示了极佳的职业前景，我们积极让本科生进入研究前沿，并将他们培养成下一代创新者。