A Program of Medium Energy Nuclear Physics

现在一个公认的事实是，核子、质子和中子--构成宇宙中绝大多数可见物质的粒子--是由更基本的称为夸克的粒子组成的。该奖项支持的主要物理项目是测量夸克在核子中的分布情况。在这种夸克形式的物质中，能量和质量根据著名的E=mc2在短时间尺度上来回交换。由该奖项支持的四名教员和他们的早期职业科学家小组将进行和领导实验，帮助我们了解夸克物质的基本特征：反物质在核子中的作用是什么？当核子内部的温度增加到很高时会发生什么？核子内部夸克的运动看起来与在时间上向前或向后移动是一样的吗？这些实验的目的是与所谓的粒子物理标准模型的理论预测进行比较，既是为了更好地理解它，也是为了寻找它没有描述的新现象的迹象。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。该计划还包括一些外联活动：为较小机构的本科生举办的暑期计划，为来自代表性不足群体的当地高中生举办的一个计划的领导力，以及每周一次的公开演讲计划，一门关于能源和可持续发展的公共课程，以及一个探索棒球物理学的流行网站。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，但我们很难提供真正基于QCD的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。这一奖项使人们能够利用ATLAS的完全改装的喷流和sPHENIX的小型碰撞系统中的关联来继续研究QGP的特性。这项QCD研究将包括四个实验：费米实验室的SeaQuest，欧洲核子研究中心的COMPASS-II和ATLAS，以及在不久的将来，布鲁克海文的SPHENIX。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实验的目标是将目前EDM的上限提高100倍。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

It is now a well-established fact that nucleons, protons and neutrons—particles that make up the vast majority of the visible matter in the Universe—are made up of more elementary particles called quarks. The main physics program supported by this award is to measure how quarks are distributed in nucleons. In this quark form of matter, energy and mass are traded back and forth on short timescales according to the famous E = mc2. The four faculty members supported by this award and their group of early career scientists will conduct and lead experiments that will help us to understand essential features of quark matter: What is the role of anti-matter in the nucleon? What happens when the temperature inside a nucleon is increased to a high value? Does the motion of the quarks inside the nucleon look the same as one moves forward or backward in time? The goal of these experiments is to compare with theoretical predictions from the so-called Standard Model of Particle Physics, both to better understand it, as well as to look for signs of new phenomena that are not described by it. 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 program also includes a number of outreach activities: summer programs for undergraduates from smaller institutions, leadership of a program for local high school students from underrepresented groups, along with a program of weekly public presentations, a public course in energy and sustainability and a popular website exploring the physics of baseball.The prevailing theory of the strong force, quantum chromodynamics or QCD, is a generalization of the highly successful QED, yet we are hard-pressed to provide truly QCD-based 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 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 award enables continued study of the QGP’s properties using fully reconstructed jets at ATLAS and correlations in small collision systems at sPHENIX. This QCD research will comprise four experiments: SeaQuest at Fermilab, COMPASS-II and ATLAS at CERN as well as, in the near future, sPHENIX at Brookhaven. 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.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.