A Program of Medium Energy Nuclear Physics

中能核物理项目

• 批准号: 1205671
• 负责人: Douglas Beck
• 金额: $ 755.5万
• 依托单位: University of Illinois at Urbana-Champaign
• 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: 2012-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1205671&HistoricalAwards=false
• 关键词: Program; Medium; Energy; Nuclear; Physics

Understanding the structure of hadrons and nuclei remains a compelling thrust in nuclear physics. Although it is a relatively straightforward generalization of quantum electrodynamics, the underlying theory of strong interactions, quantum chromodynamics (QCD), is difficult to solve, especially in the context of structure. Although lattice QCD has made important progress, observations are clearly still important to make the theory's phenomena come to life. The University of Illinois at Urbana-Champagne program focuses on the spin and flavor structure of the nucleon in a variety of experiments at high energies where key elements of the microscopic role of quarks, anti-quarks and gluons are poorly understood. The PHENIX polarized pp program, while continuing to measure the contribution of gluons to the nucleon spin, will enter a new phase of measuring the contributions of antiquarks, taking advantage of an Illinois-led muon trigger upgrade. The SEAQUEST experiment at Fermilab will follow on the very successful E866 measurement of the intriguing asymmetry of up and down anti-quarks in the nucleon with more precise data over a broader kinematic range. The Illinois group has recently joined the fixed target COMPASS experiment at CERN, where they will make a major contribution to an apparatus upgrade that will take the next step in characterizing the transverse spin structure of the nucleon. Together, these efforts - with substantial Illinois contributions - promise significant advances in the understanding of QCD. Beyond the current standard model of particle physics must lie new phenomena, only the shadows of which are currently visible. The Illinois group contributes to these investigations through low-energy experiments designed to follow the leads provided by certain non-standard-model phenomena. In the neutrino sector, where even the existence of non-zero masses was a surprise not contemplated in the standard model, the Illinois group is working on the Daya Bay experiment. Currently taking its first data, Daya Bay will make the world's most sensitive determination of the mixing of the first and third neutrino generations, theta_(13). In the standard model, the violation of the combined charge-conjugation and parity (CP) symmetry is added 'by hand' and is not well-understood. A new measurement of the neutron's electric dipole moment (EDM), which violates CP, aims at a 100-fold improvement compared with the present limit. These measurements are important on their own merits, but may also shed light on the observed asymmetry of matter and anti-matter in the universe. The existence of this asymmetry is thought to require more CP violation than is currently known, and may arise from interactions that would generate an EDM in the neutron, and or in the neutrino sector where it would manifest in CP-violating mixing between the first and third generations. The Illinois group has reached beyond its laboratories to make significant contributions to education and outreach and will continue to do so. Research projects contribute substantially to the education of a large number of postdoctoral research associates, graduate, and undergraduate students. The faculty are also involved in innovative curricular and outreach efforts. Examples include introduction of research equipment and measurement protocols into advanced modern physics laboratories, establishment of a graduate option in energy and sustainability engineering, inventing new inter-disciplinary math/engineering teaching protocols targeted directly at retention, continued support of a Saturday lecture program aimed primarily at high school students, and a major contribution to the Physics of Baseball, a topic having wide public interest. Our group and Department expect to continue to support strongly the participation of underrepresented groups, for example, acting as host for the Conference for Undergraduate Women in Physics in 2008.

理解强子和原子核的结构仍然是核物理学中一个引人注目的推动力。 虽然它是量子电动力学的一个相对简单的推广，但强相互作用的基础理论，量子色动力学（QCD），很难解决，特别是在结构的背景下。 尽管格点QCD已经取得了重要的进展，但观测显然对于使理论的现象变得真实仍然很重要。 伊利诺伊大学厄巴纳-香槟分校的项目重点是在各种高能实验中核子的自旋和味道结构，其中夸克，反夸克和胶子的微观作用的关键要素知之甚少。 PHENIX极化pp计划在继续测量胶子对核子自旋的贡献的同时，将利用伊利诺斯州领导的μ子触发升级进入测量反夸克贡献的新阶段。 费米实验室的SEAQUEST实验将在非常成功的E866测量核子中上下反夸克的有趣不对称性之后，在更广泛的运动学范围内获得更精确的数据。 伊利诺斯州的小组最近加入了欧洲核子研究中心的固定目标COMPASS实验，在那里他们将为设备升级做出重大贡献，该设备升级将在表征核子的横向自旋结构方面迈出下一步。 总之，这些努力-与伊利诺伊州的实质性贡献-承诺在量子色动力学的理解显着进步。 在当前粒子物理学的标准模型之外，一定存在着新的现象，目前只能看到这些现象的影子。 伊利诺伊州小组通过低能实验为这些研究做出了贡献，这些实验旨在跟踪某些非标准模型现象提供的线索。 在中微子部分，即使非零质量的存在也是一个标准模型中没有考虑到的惊喜，伊利诺斯州的小组正在进行大亚湾实验。 大亚湾核电站目前正在获取第一批数据，它将对第一代和第三代中微子θ_（13）的混合进行世界上最灵敏的测定。 在标准模型中，电荷共轭和宇称（CP）对称性的破坏是“手工”添加的，并且没有得到很好的理解。 一种新的测量中子的电偶极矩（EDM），这违反了CP，旨在提高100倍，与目前的限制相比。 这些测量本身就很重要，但也可能揭示宇宙中物质和反物质的不对称性。 这种不对称性的存在被认为需要比目前已知的更多的CP破坏，并且可能来自于在中子中产生EDM的相互作用，或者在中微子扇区中，它将在第一代和第三代之间的CP破坏混合中表现出来。 伊利诺伊州的小组已经超越了其实验室，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助理，研究生和本科生的教育做出了重大贡献。 教师也参与创新课程和推广工作。例如，将研究设备和测量协议引入先进的现代物理实验室，建立能源和可持续发展工程的研究生选项，发明新的跨学科数学/工程教学协议，直接针对保留，继续支持主要针对高中生的周六讲座计划，以及对棒球物理学的重大贡献，这是一个具有广泛公众兴趣的话题。我们的小组和部门希望继续大力支持代表性不足的群体的参与，例如，担任2008年物理学本科女生会议的东道主。