RUI: Precision Weak Interaction Studies in Nuclei

RUI：原子核中的精确弱相互作用研究

• 批准号: 1506084
• 负责人: Paul Voytas
• 金额: $ 18万
• 依托单位: Wittenberg University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506084&HistoricalAwards=false
• 关键词: RUI; Precision; Weak; Interaction; Studies

The research supported by this award will probe the limits of our understanding of the weak interaction, one of the four fundamental forces of nature. Among other things, the weak interaction is responsible for the type of radioactive decay called beta decay in which a nucleus is transformed into a different nucleus with the emission of an electron and a neutrino. The award will allow the two scientists to carry out experiments in which they precisely measure the energy of electrons emitted in four different nuclear beta decays. Three of these experiments will test key aspects of the Standard Model of the electroweak interaction, which is the theory that describes the unification of two of the fundamental forces, the weak interaction and the electromagnetic interaction. These precision beta decay measurements are complementary to particle collider experiments in the search for new physics. A fourth proposed experiment aims to resolve uncertainties in the beta decay of potassium-40, an important tool in geochronology. The research program has the further goal and benefit of training highly talented undergraduate physics students. Students involved will gain experience with state-of-the-art software and experimental techniques, and will learn to think independently and gain a variety of practical problem solving skills. The broader impact is felt when these students enter the workforce in STEM fields or in teaching. The research program consists of several experiments involving the high precision measurement of the shapes of beta spectra. In two of the proposed experiments the goal is to provide a strong test of the Conserved Vector Current hypothesis in the electroweak sector of the Standard Model of particle physics. In a third experiment, the goal is to improve limits on non-Standard-Model contributions (Fierz terms) to the description of the weak interaction. A fourth experiment has the goal of resolving an uncertainty in the potassium-40 beta spectrum, which is relevant to applications in geochronology. Specifically, the carbon-14 beta spectrum will be measured using a new magnetic spectrometer at the University of Wisconsin-Madison. This spectrometer will be nearly identical in form to the superconducting spectrometer used to make the same measurement in oxygen-14, enabling reduced uncertainties arising from higher order matrix element contributions. Measurements in fluorine-20 and helium-6 will be carried out at the National Superconducting Cyclotron Laboratory using implantation into a scintillator detector, which will have significantly different systematic effects from the magnetic spectrometer measurements and will be important in achieving low thresholds. A fourth experiment has the goal of measuring the shape of the potassium-40 beta spectrum. Knowledge of this spectrum shape is important for a standard technique in radioactive dating of geologic samples, but a recent report suggests the shape may not be as well understood as had been thought. An important aspect of all these measurements is in assessing and correcting for systematic effects through measurement and computational modeling.

该奖项支持的研究将探索我们对自然界四大基本力之一的弱相互作用的理解的局限性。 除此之外，弱相互作用是导致称为β衰变的放射性衰变类型的原因，在β衰变中，一个原子核通过发射一个电子和一个中微子而转变为另一个原子核。 该奖项将允许这两位科学家进行实验，精确测量四种不同的核β衰变中发射的电子能量。其中三个实验将测试电弱相互作用标准模型的关键方面，该理论描述了两种基本力，弱相互作用和电磁相互作用的统一。这些精确的β衰变测量是对粒子对撞机寻找新物理实验的补充。第四个拟议的实验旨在解决钾-40 β衰变的不确定性，钾-40是地质年代学的重要工具。该研究项目具有培养高素质物理本科人才的进一步目标和效益。参与的学生将获得最先进的软件和实验技术的经验，并将学会独立思考，获得各种实际问题解决技能。当这些学生进入STEM领域或教学领域的劳动力队伍时，会感受到更广泛的影响。该研究计划包括几个实验，涉及高精度测量β谱的形状。在两个拟议的实验中，目标是在粒子物理学标准模型的电弱部分中对守恒矢量电流假设进行强有力的检验。在第三个实验中，目标是改善非标准模型贡献（Fierz项）对弱相互作用描述的限制。第四个实验的目标是解决钾-40 β光谱的不确定性，这与地质年代学的应用有关。具体来说，碳-14 β光谱将使用威斯康星大学麦迪逊分校的一种新的磁光谱仪进行测量。该谱仪在形式上与用于在氧-14中进行相同测量的超导谱仪几乎相同，从而能够降低由高阶矩阵元素贡献引起的不确定性。氟-20和氦-6的测量将在国家超导回旋加速器实验室使用植入闪烁体探测器进行，这将具有与磁分光计测量显著不同的系统效应，并且对于实现低阈值非常重要。第四个实验的目标是测量钾-40 β光谱的形状。对于地质样品放射性测年的标准技术来说，了解这种光谱形状是很重要的，但最近的一份报告表明，这种形状可能没有想象的那么好理解。所有这些测量的一个重要方面是通过测量和计算建模来评估和纠正系统效应。