Precision Measurement of the Parity-Violating Asymmetryin e-2H Deep Inelastic Scattering

e-2H 深部非弹性散射中宇称破缺不对称性的精确测量

• 批准号: 0653347
• 负责人: Xiaochao Zheng
• 金额: $ 28.5万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-15 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0653347&HistoricalAwards=false
• 关键词: Precision; Measurement; Parity; Violating; Asymmetryin

This project will measure the parity-violating asymmetry in electron-deuterium deep inelastic scattering (PV-DIS) using the 6 GeV electron beam at the Thomas Jefferson National Accelerator Facility (JLab). The parity symmetry of nature is a fundamental property of the electromagnetic and strong interactions but was found to be violated in weak interactions in 1957. Since then, the phenomenon of parity violation has been widely used to study both the Standard Model of electro-weak interactions and the nucleon structure. Most parity violating scattering experiments so far, however, were carried out in the elastic scattering regime where the nucleon reacts as a rigid body. A remarkable feature of deep inelastic scattering is that in this regime the nucleon breaks down to its fundamental constituents -- quarks and gluons -- thus different aspects of electroweak interaction or nucleon structure can be revealed. More specifically, our goal is to extract the coupling coefficients C2q, which measures the product of the strengths of the electro-weak interactions between an electron and the Z0 boson and that between a quark and the Z0, and improve its precision to eight times better than the current published value. Such result would shed light on possible new physics beyond the current electroweak Standard Model and is complementary to other low and medium-energy Standard Model test experiments. In the near future, the PVDIS measurement will be extended after the JLab upgrade and a broad range of topics on electro-weak physics and the nucleon structure, including a potential new discovery by directly observing the charge-symmetry violation at the quark level, will be explored.The PI is playing a leading role in this project as a spokesperson. She is leading the effort to construct a new data acquisition system required for the experiment. This hardware development will provide valuable training and research experience for summer undergraduate and graduate students. This experiment will become the Ph.D. project for at least one graduate student from UVa. In the long term, the 6 GeV measurement forms the basis for the PI to develop a larger-scale (possibly international) collaboration to carry out extension of this program at the 12 GeV energy upgraded JLab.

该项目将在托马斯·杰斐逊国家加速器设施（JLab）使用6 GeV电子束测量电子-氘深度非弹性散射（PV-DIS）中的奇偶违反不对称性。自然界的宇称对称性是电磁和强相互作用的基本性质，但在1957年被发现在弱相互作用中被打破。从那时起，宇称违反现象被广泛应用于研究电弱相互作用的标准模型和核子结构。然而，到目前为止，大多数违反宇称的散射实验都是在核子作为刚体反应的弹性散射区进行的。深度非弹性散射的一个显著特征是，在这种状态下，核子分解为其基本成分——夸克和胶子——因此可以揭示电弱相互作用或核子结构的不同方面。更具体地说，我们的目标是提取耦合系数C2q，它测量电子与Z0玻色子之间的电弱相互作用强度的乘积，以及夸克与Z0之间的相互作用强度，并将其精度提高到目前公布值的8倍。这样的结果将揭示超越当前电弱标准模型的可能的新物理学，并与其他中低能量标准模型测试实验相补充。在不久的将来，在JLab升级之后，PVDIS测量将得到扩展，并将探索关于电弱物理和核子结构的广泛主题，包括通过直接观察夸克水平上的电荷对称违反的潜在新发现。PI作为发言人在这个项目中发挥主导作用。她正在领导构建实验所需的新数据采集系统。这种硬件开发将为暑期本科生和研究生提供宝贵的培训和研究经验。该实验将成为至少一名UVa研究生的博士项目。从长远来看，6 GeV的测量构成了PI发展更大规模（可能是国际）合作的基础，以在12 GeV能源升级的JLab上进行该计划的扩展。