Experimental Nuclear Physics and Fundamental Interactions at Indiana University

印第安纳大学布鲁明顿分校的实验核物理小组测量亚原子粒子和系统的性质，特别强调对称性的破坏，这可能会导致新的力和效应。这项工作围绕以下四个问题展开：质子自旋的起源是什么？实验表明，与预期相反，夸克自旋只携带了总自旋的一小部分。胶子，强力的载体，以及质子内部夸克的轨道运动是唯一的其他可能性。我们使用布鲁克海文国家实验室的高能极化质子-质子碰撞来测量胶子对质子自旋的贡献，并寻找关于夸克轨道运动的信息。为什么大爆炸结束后留下的物质比反物质多？宇宙膨胀中的物质和反物质是以相等的数量产生和湮灭的，除非存在依赖于时间方向的过程。时间反转破坏也引起了基粒子自旋轴上正负电荷的自发分离。对这种分离的探索正在进行中，使用电场在石榴石晶体中诱导块状物质磁化，并使在液氦浴中捕获的中子的自旋轴前进。中微子的性质和相互作用是什么？这些在原子核和粒子衰变过程中形成的难以捉摸的粒子可以在飞行过程中从一种类型转变为另一种类型。费米实验室MiniBooNE探测器在低能量下的新数据似乎表明，这种变化不符合由已知夸克和轻子数量建立的标准模式。比较中微子和反中微子效应并测量中微子引发的反应的工作正在进行中。我们还将检查中微子是否是它们自己的反粒子。弱力的部分有多强？这种力会导致核β衰变和其他违反镜像对称性的核反应。实验正在准备寻找来自中子-质子俘获的光子的镜面不对称性，以及当中子自旋通过液氦时的螺旋形运动。我们还建议测量中子本身的寿命和衰变特性。我们通过开放参观、实验室参观、科学咖啡馆讨论和本地公共媒体的新闻，分享从这项工作中获得的知识和我们在科学研究方面的经验。我们致力于通过参观科学课程、进行职业介绍、评判科学博览会项目、参加科学奥林匹克竞赛活动以及在印第安纳州博览会上进行物理演示来唤起当地学校系统中学生对科学的兴趣。我们通过培养博士后研究助理、研究生、本科生和高中生，为工业培养下一代科学家、教育工作者和受过技术培训的人。我们组织核物理及其各种专业的暑期班。凭借拥有自己的加速器套件的实验室提供的资源，我们还提供了新的探测器和实验技术，以许多大学院系无法企及的方式，扩大了全国各地的研究可能性。我们与密歇根大学健康质子治疗中心的质子束癌症治疗设施共享这一技术基础，该中心已经治疗了1000多名患者，工作人员中有一部分是我们以前的学生和博士后。

The experimental nuclear physics group at Indiana University-Bloomington measures the properties of sub-atomic particles and systems with a special emphasis on the breaking of symmetries that might lead to new forces and effects. This work is organized around the following four questions:What is the origin of the spin of the proton? Experiments show that, contrary to expectation, the quark spins carry a small fraction of the total. Gluons, the carriers of the strong force, and the orbital motion of quarks inside the proton are the only other possibilities. We use high-energy polarized proton-proton collisions at the Brookhaven National Laboratory to measure the gluon contribution to the proton spin and also search for information on the quark's orbital motion.Why is more matter than antimatter left over after the end of the Big Bang? Matter and antimatter in the expansion of the universe are created and annihilated in equal amounts unless processes exist which depend on the direction of time. Time reversal violation also gives rise to the spontaneous separation of positive and negative electric charge along the spin axis of fundamental particles. Searches for such a separation are underway using an electric field to induce a bulk matter magnetization in a garnet crystal and to precess the spin axis of neutrons captured in a liquid helium bath.What are the properties and interactions of neutrinos? These elusive particles formed during nuclear and particle decay can change in flight from one type to another. New data at low energies from the MiniBooNE detector at Fermilab seem to indicate that such changes do not fit into the standard pattern established by the number of known quarks and leptons. Work to compare neutrino and anti-neutrino effects and measure neutrino-induced reactions is underway. We will also check to see if neutrinos are their own anti-particles.How strong are the parts of the weak force? This force causes nuclear beta decay and other nuclear reactions that violate mirror symmetry. Experiments are in preparation to search for mirror-asymmetry in the photons from neutron-proton capture and for a corkscrew motion of neutron spins as they travel through liquid helium. We also propose to measure the lifetime and decay properties of the neutron itself.We share the knowledge gained by this work and our experiences in scientific research through Open Houses, laboratory tours, science café discussions, and news items in the local public media. We strive to awaken the interest of students in the local school system in science by visiting science classes, conducting career presentations, judging science fair projects, participating in events at the Science Olympiad, and performing physics demonstrations at the Indiana State Fair. We prepare the next generation of scientists, educators, and technically-trained people for industry by educating post-doctoral research assistants, graduate students, undergraduates, and high school students. We organize summer schools for nuclear physics and its various specialties. With the resources available at a laboratory with its own suite of accelerators, we also provide new detectors and experimental technologies that expand the research possibilities across the nation in ways that are beyond the reach of many university departments. We share this technology base with a proton beam cancer treatment facility at the IU Health Proton Therapy Center, which has treated more than 1000 patients with a staff composed in part of our former students and postdocs.