A Program of Medium Energy Nuclear Physics

美国国家科学基金会支持的中能核物理计划将使伊利诺伊大学厄巴纳-香槟分校的核物理小组继续领导和促进国际核物理研究中的高影响力实验。该研究计划有两个中心主题，即1）核子和原子核的结构和相互作用; 2）基本对称性和标准模型的检验。具体活动包括已建立的国际实验：G 0、爱马仕、PHENIX、RCS、Muon g-2、Lan和Cap。 此外，该小组还在氢原子宇称破坏（H-APV）方面进行了本地可行性研究，并正在帮助开发新的中子电偶极矩（n-EDM）实验。 所有这些实验的目标是帮助回答亚原子物理学中的重要问题。 例如，在G 0、爱马仕、RCS和PHENIX自旋程序中，一个常见的问题是“质子是如何建立的？“这些实验使用不同的工具，如宇称违反电子散射，极化电子-核子散射，真实的康普顿散射和极化质子-质子碰撞，以发现组成夸克，海夸克和胶子（部分子）在质子的众所周知的性质中所起的作用。 这些实验应该有助于解决关于质子如何获得半整数自旋的争论。 他们还将揭示质子内部不同类型夸克的相对重要性，例如，奇怪的夸克如何对质子的电荷和磁结构做出贡献。 在RHIC的PHENIX计划中，还将研究氘-核碰撞，以研究部分子在核中的作用。 Muon g-2、H-APV和n-EDM的活动都是针对第二个主题，提出的问题是“当前的标准模型正确吗？“这些努力中最成熟的g-2已经提供了令人兴奋和暗示性的证据，表明可能需要某种类型的标准模型扩展。这项工作的完成和可能的扩展将为新物理学提供一个非常严格的限制，或者强烈表明它必须存在。 ULan和UCap实验中还提供了其他基本参数的精密测量。 其中第一个将确定μ子寿命的精度为百万分之一，然后可以解释为弱相互作用强度的确定提高了20倍。 第二个实验将精确测量质子最不知名的弱形状因子（gP）。 这将为建立在低能强相互作用基本对称性基础上的精确理论预测提供严格的检验。除了直接的物理研究成果，该小组已经超越了实验室，为教育和推广做出了重大贡献，并将继续这样做。 研究项目为大量博士后、研究生和本科生的教育做出了重大贡献。

UIUC PROJECT ABSTRACTThe NSF-supported Program of Medium Energy Nuclear Physics will allow the nuclear physics group at the University of Illinois at Urbana-Champaign to continue to lead and contribute to high-impact experiments in international nuclear physics research. The research program fea-tures two central themes, namely 1) The structure and interactions of nucleons and nuclei; and 2) Tests of fundamental symmetries and the standard model. Specific activities include the estab-lished international experiments: G0, HERMES, PHENIX, RCS, Muon g-2, Lan, and Cap. Additionally, the group has a local feasibility effort in hydrogen atomic parity violation (H-APV) and is helping to develop a new neutron electric dipole moment (n-EDM) experiment. The goal of all of these experiments is to help answer important questions in subatomic physics. For ex-ample, in G0, HERMES, RCS and the PHENIX spin program, a common query is "How is the proton built?" The experiments use different tools such as parity-violating electron scattering, polarized electron-nucleon scattering, real Compton scattering, and polarized proton-proton col-lisions to discover the roles that constituent quarks, sea quarks and gluons (the partons) play to result in the well-known properties of the proton. The experiments should help settle the debate about how the proton obtains its half-integer spin. They will also shed light on the relative im-portance of different types of quarks inside the proton revealing, for example, how strange quarks contribute to the proton's charge and magnetic structure. In the PHENIX program at RHIC, deuteron-nuclei collisions will also be studied to investigate the role that partons play in nuclei. The Muon g-2, H-APV, and n-EDM activities are all aimed at the second theme, asking the question "Is the current standard model correct?" The most mature of these efforts, g-2, has already provided exciting and suggestive evidence that some type of standard model extension might be required. Completion of this effort and possible extensions will provide either a very stringent limit on new physics or, alternatively, a strong indication that it must be present. Other precision measurements of fundamental parameters are featured in the ULan and UCap experi-ments. The first of these will determine the muon lifetime to a precision of one part per million, which can then be interpreted as a 20-fold improvement in the determination of the weak interac-tion strength. The second experiment will accurately measure the least-well-known weak form factor (gP) of the proton. This will provide a stringent test of precise theoretical predictions founded on basic symmetries of strong interactions at low energies. In addition to direct physics research out-comes, the group has reached beyond the laboratory to make significant contributions to educa-tion and outreach and will continue to do so. Research projects contribute substantially to the education of a large number of postdocs, graduate, and undergraduate students.