Fundamental Studies in Nuclear Physics

核物理基础研究

• 批准号: 1812340
• 负责人: Bradley Filippone
• 金额: $ 218.4万
• 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: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1812340&HistoricalAwards=false
• 关键词: Fundamental; Studies; Nuclear; Physics

To search for new laws of nature beyond our current understanding researchers can use very high energy accelerators, such as the Large Hadron Collider at CERN, or alternatively they can make precise experimental measurements of basic particle properties and search for deviations from the known physical laws. This award supports research that centers around experiments making precise measurements of physical properties of the free neutron. In the UCNA (Ultra-Cold Neutron Asymmetry) experiment, carried out at the Los Alamos National Laboratory, extremely slow neutrons are used, which have such low energy that they can be trapped and studied. This allows the scientists to make a precise measurement of the radioactive decay of the neutron into a proton, an electron and a particle called an anti-neutrino. This provides needed information about the theory of radioactivity (also called the weak nuclear force) as well as looking for small deviations from the known physical laws as a signature of new physics. In addition, this group is leading the development of equipment for a very sensitive experiment to search for the electric dipole moment (EDM) of the neutron. The existence of this EDM would be a signal of new physics beyond our current knowledge and could help to explain why the observed universe is dominated by matter. Our present Standard Model of particle physics predicts that there should be nearly equal amounts of matter and antimatter in today's universe, which is not observed. This remains one of the great puzzles in our basic understanding of the evolution of our universe. Participation by postdoctoral scholars, graduate students, and undergraduates 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.This project is primarily focused on experimental research addressing fundamental properties of the free neutron. In particular the group will continue analyzing data from the UCNA experiment, in particular searching for new scalar and tensor forces not present in our present understanding of particle interactions. The group is also constructing experimental equipment for a new, highly sensitive experiment to search for the neutron's EDM. New results from the UCNA experiment will provide a sensitive search for new scalar or tensor components in the weak force, the so-called Fierz interference, by comparing the energy dependence of both the beta-decay asymmetry and the electron energy spectra simultaneously to further improve the sensitivity. The PI and his group are also collecting data for an improved measurement of the neutron lifetime using UCN at the Los Alamos UCN facility and anticipate results from both of these projects during the period of this grant. The PI plays a leading role in the development and construction of a new experiment searching for the electric dipole moment of the free neutron. The goal of the new neutron Electric Dipole Moment experiment - nEDM - at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is to improve the sensitivity of the measurement by two orders of magnitude compared to previous work. The observation of a neutron electric dipole moment signals violation of time-reversal 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 for it. The critical cryogenic magnets and magnetic shielding of the experiment will be commissioned at Caltech and should receive the first cold-neutron beam at SNS for neutron polarization studies during the period of this proposed grant.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.

为了寻找超出我们目前理解的新自然规律，研究人员可以使用非常高能量的加速器，如欧洲核子研究中心的大型强子对撞机，或者他们可以对基本粒子属性进行精确的实验测量，并寻找与已知物理定律的偏差。该奖项支持以实验为中心的研究，这些实验精确地测量了自由中子的物理性质。在洛斯阿拉莫斯国家实验室进行的UCNA(超冷中子不对称)实验中，使用了极慢的中子，这些中子的能量非常低，可以被捕获和研究。这使得科学家们能够精确地测量中子在质子、电子和反中微子粒子中的放射性衰变。这提供了有关放射性理论(也称为弱核力)的必要信息，以及寻找与已知物理定律的微小偏差作为新物理学的标志。此外，该小组正在领导一项非常灵敏的实验设备的开发，以寻找中子的电偶极矩(EDM)。这种EDM的存在将是我们目前所知之外的新物理学的信号，并有助于解释为什么观测到的宇宙由物质主导。我们目前的粒子物理标准模型预测，在今天的宇宙中，应该有几乎相等数量的物质和反物质，而这是没有观测到的。这仍然是我们对宇宙演化的基本理解中的一大谜题。博士后学者、研究生和本科生的参与是研究计划的重要组成部分，为年轻研究人员提供了在这一核物理前沿领域推进他们的培训和教育的难得机会。该项目主要专注于解决自由中子基本性质的实验研究。特别是，该小组将继续分析来自UCNA实验的数据，特别是寻找我们目前对粒子相互作用的理解中没有的新的标量和张量力。该小组还在为一项新的、高灵敏度的实验建造实验设备，以寻找中子的EDM。UCNA实验的新结果将提供对弱力中新的标量或张量分量的灵敏搜索，即所谓的Fierz干涉，通过同时比较β衰变不对称性和电子能谱的能量相关性，进一步提高灵敏度。PI和他的小组还在收集数据，以便使用洛斯阿拉莫斯UCN设施的UCN改进对中子寿命的测量，并预计在这笔赠款期间这两个项目的结果。PI在探索自由中子电偶极矩的新实验的发展和建设中起着主导作用。橡树岭国家实验室散裂中子源的新的中子电偶极矩实验-nEDM-的目标是将测量的灵敏度比以前的工作提高两个数量级。对中子电偶极矩的观测表明它违反了时间反转对称性，并可能提供与宇宙物质-反物质不对称的起源以及导致这种不对称性的新物理现象有关的重要信息。该实验的关键低温磁体和磁屏蔽将由加州理工学院委托进行，并应在本拟议授权期间在SNS获得第一个用于中子极化研究的冷中子束。该奖励反映了NSF的法定使命，并已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。

项目成果

Impact of O16(γ,α)C12 measurements on the C12(α,γ)O16 astrophysical reaction rate

O16(γ,α)C12 测量对 C12(α,γ)O16 天体物理反应速率的影响

• DOI: 10.1103/physrevc.99.055802
• 发表时间: 2019
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: Holt, R. J.;Filippone, B. W.;Pieper, Steven C.
• 通讯作者: Pieper, Steven C.

CP -violating dark photon interaction

CP破坏暗光子相互作用

• DOI: 10.1103/physrevd.101.075016
• 发表时间: 2020
• 期刊: Physical Review D
• 影响因子: 5
• 作者: Fuyuto, Kaori;He, Xiao-Gang;Li, Gang;Ramsey-Musolf, Michael
• 通讯作者: Ramsey-Musolf, Michael

Cavallo's multiplier for in situ generation of high voltage

• DOI: 10.1088/1748-0221/13/05/p05017
• 发表时间: 2018-03
• 期刊: Journal of Instrumentation
• 影响因子: 1.3
• 作者: S. Clayton;T. Ito;J. Ramsey;Wen Wang;Matej Blatnik;B. Filippone;G. Seidel

Final results for the neutron β -asymmetry parameter A 0 from the UCNA experiment

UCNA 实验中子 β 不对称参数 A 0 的最终结果

• DOI: 10.1051/epjconf/201921904004
• 发表时间: 2019
• 期刊: EPJ Web of Conferences
• 作者: Plaster, B.;Adamek, E.;Allgeier, B.;Anaya, J.;Back, H.O.;Bagdasarova, Y.;Berguno, D.B.;Blatnik, M.;Boissevain, J.G.;Bowles, T.J.
• 通讯作者: Bowles, T.J.

Designing electrode profiles with the equipotential method

• DOI: 10.1016/j.elstat.2021.103550
• 发表时间: 2021
• 期刊: Journal of Electrostatics
• 影响因子: 1.8
• 作者: Wanchun Wei