A Program of Medium Energy Nuclear Physics

现在一个公认的事实是，核子、质子和中子是由更基本的称为夸克的粒子组成的。这项拨款支持的主要物理计划是测量夸克在核子中的分布，特别是夸克的磁矩与核子的磁矩如何对齐？S总磁矩。过去十年的测量表明，夸克只贡献了核子总自旋的三分之一左右，这导致了预测，很大一部分来自夸克和其他来源的轨道运动。这些实验的目的是将夸克分布(及其轨道运动)的结果与所谓的粒子物理标准模型的理论预测进行比较。寻找中子电偶极矩的额外测量也是该项目的一部分，这将是一个超越粒子物理标准模型的物理信号，标准粒子物理模型描述了构成宇宙中大多数可见物质的基本粒子的性质。这些研究工作将有助于对博士后、研究生和本科生进行先进高科技劳动力所需的广泛技能的教育。流行的强力理论，量子色动力学或QCD，是非常成功的QED的概括，但QCD很难提供对核子结构的定量或直观描述。该项目将重点研究质子的关键性质，目标是测量不佳的海夸克和未知的夸克轨道运动。这项研究将在四个实验中进行：费米实验室的SeaQuest，布鲁克海文的PHENIX，以及欧洲核子研究中心的COMPASS-II和ATLAS。这股强大的力量也在时间之初发挥了作用。在大爆炸的早期阶段，夸克-胶子等离子体(QGP)在强大的作用力将夸克限制在束缚态之前，曾存在过一瞬间。这种转瞬即逝的物质状态已经在实验室中被重现，并被发现具有非凡的性质，例如粘度如此之低，以至于可能达到理论上的最低值。这项资助使我们能够利用ATLAS的完全重建的喷流和PHENIX的小碰撞系统中的关联，继续研究QGP？S的性质。该奖项还支持寻找中子的永久电偶极矩(EDM)，这是一个违反CP的量。NEDM实验的目标是比以往实验设定的目前EDM上限提高100倍。

It is now a well-established fact that nucleons, protons and neutrons, are made up of more elementary particles called quarks. The main physics program supported by this grant is to measure how quarks are distributed in nucleons and in particular how the magnetic moments of quarks are aligned compared with the nucleon?s overall magnetic moment. Measurements over the past decade have shown that the quarks contribute only about 1/3 of the total spin of the nucleon, which gives rise to prediction that a significant fraction comes from the orbital motion of the quarks and other sources. The goal of these experiments is to compare results on the quark distributions (and their orbital motion) with theoretical predictions from the so-called Standard Model of Particle Physics. Additional measurements to search for an electric dipole moment of the neutron, which would be a signal of physics beyond the Standard Model of particle physics, which describes the properties of the elementary particles making up most of the visible matter in the universe, are also part of this project. These research efforts will contribute to the education of postdocs, graduate students, and undergraduates in a broad array of skills needed in the advanced high tech workforce.The prevailing theory of the strong force, Quantum Chromodynamics or QCD, is a generalization of the highly successful QED, yet QCD is hard pressed to provide either quantitative or intuitive descriptions of nucleon structure. This project will focus on investigating key properties of the proton, targeting the poorly measured sea quarks and the unknown orbital motion of the quarks. The research will be performed at four experiments: SeaQuest at Fermilab, PHENIX at Brookhaven, and COMPASS-II and ATLAS at CERN. The strong force also played a role at the beginning of time. In the early stages of the big bang, the quark-gluon plasma (QGP) existed for an instant, before the strong force confined the quarks into bound states. This fleeting state of matter has been recreated in the laboratory and found to possess extraordinary properties, such as a viscosity so low that it may be at its theoretical minimum. This grant enables continued study of the QGP?s properties using fully reconstructed jets at ATLAS and correlations in small collision systems at PHENIX. This award also supports a search for a permanent electric dipole moment (EDM) of the neutron, a CP-violating quantity. The nEDM experiment aims at a 100-fold improvement over the present upper limit of the EDM set by previous experiments.