Precise Measurement of the Ratio of (V-A) Coupling Constants in Free Neutron Beta Decay and Search for Non-Standard Model Couplings with the Nab and pNab Spectrometers

使用 Nab 和 pNab 谱仪精确测量自由中子 Beta 衰变中的 (V-A) 耦合常数比并搜索非标准模型耦合

• 批准号: 2111363
• 负责人: Stefan Baessler
• 金额: $ 48.5万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2111363&HistoricalAwards=false
• 关键词: Precise; Measurement; Ratio; Coupling; Constants

This grant supports the measurement of angular correlation coefficients describing neutron beta decay using the “Nab” spectrometer at Oak Ridge National Laboratory. In this experiment the "a" and "b" coefficients describe the proton and electron resulting from the decay of the neutron. The main purpose of the measurements is to test the Standard Model of Nuclear and Particle Physics, which has been extremely successful in describing most of the properties and behavior of the elementary particles to date but leaves open critical questions such as the reason for the dominance of matter over anti-matter in the universe. A discovery of Beyond the Standard Model physics would thus have important implications for Physics and Cosmology. Installation of the Nab spectrometer at the Spallation Neutron Source (SNS) at Oak Ridge will be finished by the end of summer 2021, and commissioning and data taking will commence and continue for the duration of the proposal period. The PI is the project manager for the Nab collaboration. This grant will fund the PI’s group, and they will participate in data taking, detector simulation, data analysis, and characterization of the proton detection efficiency. The PI is strongly committed to attracting members of underrepresented groups. The University of Virginia physics department recently became a new site for the APS bridge program, and the PI is serving as a mentor. Furthermore, the project has a valuable impact on higher education: most of the work is done by students at undergraduate and graduate level, and these students will earn valuable skills and experiences for their future careers.The redundancy inherent in the Standard Model description of the neutron beta decay process allows for sensitive checks of the model’s validity. One of the expected observables (the neutrino-electron-correlation coefficient “a”) will allow an extraction of 𝑉𝑢𝑑, the upper left element of the Cabbibo-Kobayashi-Maskawa (CKM) matrix, in order to test the unitarity of the matrix. A recent re-evaluation of the world’s data suggests that CKM matrix unitarity is violated and so the results of the Nab experiment are eagerly anticipated. The other observable (The Fierz term “b”) allows us to test for scalar or tensor interactions at low energies, in a complementary way, and with sensitivity competitive to what is expected from the LHC. The current Long Range Plan for Nuclear Science devotes a paragraph to this effort (see LRP, page 75).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.

该赠款支持使用Oak Ridge国家实验室的“ NAB”光谱仪来测量角相关系数衰减。在本实验中，“ A”和“ B”系数描述了由中子的衰减产生的质子和电子。测量值的主要目的是测试核和粒子物理学的标准模型，在描述迄今为止的基本粒子的大多数特性和行为方面非常成功，但留下了开放的关键问题，例如宇宙中物质优势占主导地位的原因。因此，发现超出标准模型物理学将对物理和宇宙学具有重要意义。在2021年夏末，将在Oak Ridge的Spallation Neutron Source（SNS）安装NAB光谱仪，调试和数据获取将开始并在提案期间继续进行。时期。 PI是NAB协作的项目经理。该赠款将资助PI的小组，他们将参与数据获取，检测器仿真，数据分析和质子检测效率的表征。 PI强烈致力于吸引代表性不足的群体的成员。弗吉尼亚大学物理系最近成为APS桥梁计划的新站点，PI正在成为一种心理。此外，该项目对高等教育具有宝贵的影响：大多数工作是由本科生和研究生层面的学生完成的，这些学生将为他们的未来职业赢得宝贵的技能和经验。中子β衰减过程的标准模型描述中继承的冗余允许对模型的有效性进行敏感检查。预期的可观察到的（神经元电子相关系数“ a”）将允许提取𝑉𝑢𝑑的cabbibo-kobayashi-maskawa（ckm）矩阵的左上元素，以测试矩阵的统一。最近对世界数据的重新评估表明，CKM矩阵统一受到侵犯，因此急切地预料了NAB实验的结果。另一个可观察到的（fierz术语“ b”）允许我们以低能，完全的方式测试标量或张量相互作用，并且具有与LHC预期的敏感性。当前的核科学远程计划为这项工作提供了一段段落（请参阅LRP，第75页）。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，通过评估被认为是宝贵的支持。

项目成果

Precision pulse shape simulation for proton detection at the Nab experiment

Nab 实验中质子检测的精确脉冲形状模拟

• DOI: 10.1103/physrevc.107.065503
• 发表时间: 2023
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: Hayen, Leendert;Choi, Jin Ha;Combs, Dustin;Taylor, R. J.;Baeßler, Stefan;Birge, Noah;Broussard, Leah J.;Crawford, Christopher B.;Fomin, Nadia;Gericke, Michael
• 通讯作者: Gericke, Michael

Measurement of the parity-odd angular distribution of γ rays from polarized neutron capture on Cl35

Cl35 极化中子俘获γ射线奇偶角分布的测量

• DOI: 10.1103/physrevc.106.015504
• 发表时间: 2022
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: Fomin, N.;Alarcon, R.;Alonzi, L.;Askanazi, E.;Baeßler, S.;Balascuta, S.;Barrón-Palos, L.;Barzilov, A.;Blyth, D.;Bowman, J. D.
• 通讯作者: Bowman, J. D.