Fundamental Studies in Nuclear Physics

核物理基础研究

• 批准号: 1205977
• 负责人: Bradley Filippone
• 金额: $ 219.61万
• 依托单位: California Institute of Technology
• 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: 2012-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1205977&HistoricalAwards=false
• 关键词: Fundamental; Studies; Nuclear; Physics

Technical Description of Project:Our project - Fundamental Studies in Nuclear Physics - at California Institute of Technology is primarily focused on experimental research addressing fundamental properties of the free neutron. In particular we will continue taking data with the UCNA experiment while also developing hardware for construction of a new, highly sensitive experiment to search for the neutron's electric dipole moment. The UCNA experiment has already produced a precision measurement of the beta-asymmetry in neutron decay using Ultra-Cold Neutrons for the first time. This quantity allows a sensitive test of the unitarity of the CKM quark-mixing matrix and has the potential to provide evidence for new physics beyond the Standard Model of particle interactions. With recent improvements to the apparatus we are poised to improve the precision on the asymmetry down to ~ 0.3% with additional data-taking and analysis during the period of this grant. The goal of the new electric dipole moment experiment - nEDM at the Spallation Neutron Source at Oak Ridge National Laboratory - is to improve the sensitivity by a factor of 100 compared to previous measurements; observation of an electric dipole moment signals violation of time-reversal and charge-parity (CP) symmetry, and could provide important information related to the origin of the matter-antimatter asymmetry of the universe and the new physical phenomena that is responsible. Non-technical Description of ProjectOur project at Caltech is primarily focused on studying fundamental properties of the free neutron. The neutron is an unstable particle and decays with a ten minute half-life into a proton, an electron and an anti-neutrino. We are making precision measurements of the neutron decay using very slow neutrons that can be stored in bottles. These measurements should allow us to make the most precise measurements of the distribution of electrons from the decay of spin-polarized neutrons. These data can push our understanding of the neutron's decay to the limits of theoretical understanding and may indicate that our current picture is incomplete and must be revised. We are also developing a new experiment to search for an electric dipole for the free neutron. An electric dipole is a separation of the plus and minus charge within this neutral particle. The existence of this dipole would signal a significant breakdown of so-called Charge-Parity (CP) symmetry. A significant breakdown of this symmetry has been suggested to explain why the universe is dominated by material composed of standard particles with virtually no anti-particles present in the universe. This puzzle (more matter than anti-matter) has stumped physicists for many years and we hope to discover and measure the neutron's electric dipole to help explain this basic property of the universe. We also note that participation by postdoctoral scholars as well as graduate and undergraduate students is an essential part of the research program, affording young researchers exceptional opportunities to advance their training and education in this frontier area of nuclear physics.

项目的技术描述：我们的项目 - 核物理学的基本研究 - 加利福尼亚理工学院主要集中于实验研究，涉及免费中子的基本属性。特别是，我们将继续通过UCNA实验获取数据，同时还开发了用于构建新的高度敏感实验的硬件，以搜索中子的电偶极矩。 UCNA实验已经首次使用超冷的中子对中子衰减中的β-对称性进行了精确测量。该数量允许对CKM夸克混合矩阵的单位性进行敏感测试，并有可能为超出粒子相互作用的标准模型以外的新物理学提供证据。随着对设备的最新改进，我们有望在本赠款期间通过额外的数据制作和分析提高不对称性的精度降至约0.3％。与以前的测量相比，新的电偶极矩实验的目标是橡树岭国家实验室的NEDM NEDM在橡树岭国家实验室的散布中子源的目标是提高灵敏度100倍。观察到电偶极矩的观察信号违反了时间逆转和电荷 - 对称性，并且可以提供与宇宙的物质抗逆点数不对称起源和负责的新物理现象有关的重要信息。加州理工学院项目项目项目的非技术描述主要集中于研究自由中子的基本属性。中子是一个不稳定的粒子，并以十分钟的半衰期腐烂到质子，电子和抗中性菌。我们正在使用可以存储在瓶中的非常缓慢的中子对中子衰减进行精确测量。这些测量应使我们能够从自旋极化中子的衰减中对电子的分布进行最精确的测量。这些数据可以将我们对中子的衰减的理解推向理论理解的局限性，并可能表明我们当前的情况是不完整的，必须进行修订。我们还正在开发一个新的实验，以寻找免费中子的电偶极子。电偶极子是该中性粒子内的加号和负电荷的分离。该偶极子的存在将表明所谓的电荷 - 元度（CP）对称性的显着崩溃。已经提出了这种对称性的重大分解，以解释为什么宇宙由宇宙中几乎不存在抗粒子的标准颗粒组成的材料主导。这个难题（比反物质更多）使物理学家陷入了多年的困扰，我们希望发现并测量中子的电偶极子，以帮助解释宇宙的基本特性。我们还注意到，博士后学者以及研究生和本科生的参与是研究计划的重要组成部分，为年轻的研究人员提供了在这个核物理学领域的培训和教育的杰出机会。