Nuclear Physics Equipment

大约98%的核子质量，也就是可见宇宙的质量，都来自于它们的组分——夸克和胶子之间的相互作用。为裸夸克提供质量的希格斯机制只占核子质量的一小部分。夸克在介子和重子内的限制是它们基本相互作用的直接结果。强核力的场论，量子色动力学（QCD），现在已经很好地建立了，但是上面描述的现象还不能从量子色动力学的拉格朗日量来理解；它们是由这些相互作用的独特复杂性产生的自然属性。在核子和原子核的质量尺度上，QCD还很棘手，因此，在这些能量下，物质基本性质的清晰图景尚不存在。然而，这种情况将会改变，未来十年的理论和实验发展都有望在QCD和标准模型的背景下彻底改变我们对核物质的理解。我们有一个雄心勃勃的工作计划，包括从现有主题发展研究方案，最近开辟的新物理测量的可能性，以及从以前获得的数据完成物理项目。我们的方案将以我们以前的综合拨款的工作为基础，我们将利用在人力和设备方面的投资，在尽可能高的水平上，在世界顶级的设施上，解决我们领域当前的问题。科学计划面临的挑战可以概括为几个关键问题，我们将它们归纳在一起，因为它们大致符合我们所定义的主题：*在强相互作用粒子（强子）中限制夸克和胶子的机制是什么？质子和中子的结构是什么？强子的质量和自旋是如何产生的？我们能从夸克-夸克相互作用中理解强子的激发谱吗？*是否存在外来强子（多夸克态、混合介子和胶球）？* QCD如何产生核力？核物质的状态方程是什么？*暗物质的本质是什么？我们将在两个世界领先的设施中通过领先的实验项目来解决这些问题：*美国弗吉尼亚州纽波特纽斯杰斐逊实验室(JLab)*德国美因茨MAMI；

Approximately 98% of the mass of nucleons, and therefore of the visible universe, emerges from the interactions among their constituents, the quarks and gluons. The Higgs mechanism, which gives mass to the bare quarks, is responsible for only a small fraction of the nucleon mass. The confinement of quarks within mesons and baryons is a direct consequence of their fundamental interactions. The field theory of the strong nuclear force, Quantum Chromodynamics (QCD), is now well established, and yet the phenomena described above cannot be understood from the QCD Lagrangian; they are emergent properties that arise from the unique complexity of these interactions. QCD is as yet intractable at the mass scale of nucleons and nuclei, so a clear picture of the fundamental nature of matter at these energies does not yet exist. However, this situation is set to change, and both theoretical and experimental developments in the coming decade are expected to revolutionise our understanding of nuclear matter within the context of QCD and the Standard Model. We have an ambitious plan of work that encompasses the development of research programmes from existing themes, possibilities for new physics measurements that have opened up recently, and the completion of physics projects from data that has been previously obtained. Our programme will build on the work of our previous consolidated grant and we will exploit the investment in manpower and equipment to address the current issues in our field at the highest possible level, at the world's top facilities. The challenges for the science programme are encapsulated by several key questions, which we group together as they roughly match the themes we have defined:* What is the mechanism for confining quarks and gluons in strongly interacting particles (hadrons)?* What is the structure of the proton and neutron, and how do hadrons get their mass and spin? * Can we understand the excitation spectra of hadrons from the quark-quark interaction? * Do exotic hadrons (multiquark states, hybrid mesons and glueballs) exist? * How do nuclear forces arise from QCD? * What is the equation of state of nuclear matter? * What is the nature of dark matter?We will address these questions by leading experimental programmes at two of the world's leading facilities:* Jefferson Lab, Newport News, Virginia, USA (JLab)* MAMI, Mainz, Germany: