Fundamental physics with cold and ultra-cold neutrons

冷和超冷中子的基础物理

• 批准号: 341298-2009
• 负责人: Gericke, Michael
• 金额: $ 9.47万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Group
• 财政年份: 2009
• 资助国家: 加拿大
• 起止时间: 2009-01-01 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=429574
• 关键词: Fundamental; physics; cold; ultra; neutrons

Among the four fundamental forces that are known to exist in nature, gravity, electromagnetism, and the strong and weak nuclear forces, only the weak interaction violates parity. When parity is violated, the results of an experiment differ from those obtained with an experiment that was set up as its mirror image. The work proposed here involves studies which use the weak interaction between subatomic particles as a probe for their fundamental properties. The experiments use high intensity neutron sources and particle accelerators to either search for very small spatial and yield asymmetries in the products of the reaction between the projectile and a given target, or to measure with high accuracy the properties of particle (i.e. neutron) decay products. The type of asymmetries we measure can only emerge as a result of the weak interaction being part of that reaction. The fact that only the weak interaction violates parity, and its short range, makes these measurements highly useful probes of very small effects inside nucleons. The currently accepted mathematical and phenomenological description of our knowledge about the interactions between subatomic particles is known as the Standard Model. Although highly successful, there are strong theoretical reasons, such as the large number of adjustable parameters, to expect that the Standard Model is a low energy effective theory of some more fundamental description of nature. A Canadian research group, consisting of the universities of Manitoba, Winnipeg, Northern British Columbia, and TRIUMF, Canada's laboratory for nuclear and particle physics, has initiated a Canadian program in fundamental neutron physics experiments to investigate the properties and possible extensions of the Standard Model. The program will consist of measurements using cold neutrons, conducted at the Spallation Neutron Source in Oak Ridge, Tennessee and of measurements using ultracold neutrons, to be conducted at TRIUMF and Los Alamos National Laboratory, New Mexico. These world-leading new facilities will permit us to carry out a program of ultra-precise measurements of weak interactions of the neutron.

在自然界中已知存在的四种基本力中，引力，电磁力，以及强核力和弱核力，只有弱相互作用违反宇称。当宇称被破坏时，实验的结果与被设置为镜像的实验所获得的结果不同。这里提出的工作涉及使用亚原子粒子之间的弱相互作用作为其基本性质的探针的研究。该实验使用高强度中子源和粒子加速器，要么搜索非常小的空间，并产生不对称的产物之间的反应的弹丸和一个给定的目标，或以高精度测量粒子（即中子）衰变产物的属性。我们测量的这种不对称性只能作为弱相互作用的一部分而出现。事实上，只有弱相互作用违反宇称，其短范围，使这些测量非常有用的探针非常小的影响核子内。目前公认的数学和现象学描述我们的知识，关于亚原子粒子之间的相互作用被称为标准模型。虽然标准模型非常成功，但有很强的理论理由，例如大量的可调参数，可以预期标准模型是一个低能有效的理论，对自然界进行了一些更基本的描述。一个由马尼托巴、温尼伯、北方不列颠哥伦比亚省和加拿大核物理和粒子物理实验室TRIUMF组成的加拿大研究小组发起了一个加拿大基本中子物理实验方案，以研究标准模型的性质和可能的扩展。该方案将包括在田纳西州橡树岭的斯普林中子源使用冷中子进行的测量，以及在新墨西哥州的TRIUMF和洛斯阿拉莫斯国家实验室使用超冷中子进行的测量。 这些世界领先的新设施将使我们能够执行一项对中子弱相互作用进行超精确测量的计划。