Electromagnentic probe of nuclear interactions

核相互作用的电磁探针

• 批准号: SAPIN-2020-00037
• 负责人: Starosta, Krzysztof
• 金额: $ 7.58万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748103
• 关键词: Electromagnentic; probe; nuclear; interactions

Low-energy nuclear physics recently underwent a significant paradigm shift in the basic understanding of its objects of study. In light and medium mass nuclei it is now possible to provide ab-initio predictions of nuclear structure inspired by the Quantum Chromodynamics (QCD) theory of strong interactions, breaking a decades-long reign of phenomenological effective interactions derived from global or local fits to experimental data. At TRIUMF, Canada's particle accelerator centre, sustained development in accelerators and gamma-ray detection systems permits the study of nuclei which are very far from stability, testing theories and understanding developed based on data obtained near stability.  A striking example is the change of nuclear shell ordering prompted by the neutron or proton excess that rearranges shell structure and breaks trends of observables such as spins/parities, masses, binding, and excitation energies established near stability. Configuration Interaction methods using two- and three-body interactions inspired by QCD allow the many-body nuclear problem to be solved for medium and heavy mass nuclei, including those far from stability, while density functional theories provide an extension for application of these interactions up to the heaviest nuclei. Current theoretical methods track approximation errors systematically, predicting trends together with uncertainties, thus enabling direct tests of QCD-inspired effective interactions through comparison to the experimental data. The long-term goal of the proposed program is to improve quantitative understanding of the interactions between nucleons (protons and neutrons) inside atomic nuclei. The short-term objective is to examine experimentally the dependence of nuclear interactions on the asymmetry between the proton number (Z) and the neutron number (N). In particular, it is proposed to execute a program of precision measurements of electromagnetic transition rates using heavy radioactive beams provided by TRIUMF while taking advantage of developments of the experimental infrastructure at Simon Fraser University (SFU). Experiments awaiting execution at TRIUMF are measurements of electromagnetic transition rates in 55Co and 55Ni which are proton- and a neutron-hole nuclei with respect to closed-shell 56Ni, and in 20Mg, the most neutron deficient isotope at Z=12. It is also proposed to study products of reactions induced by fast neutrons, as well as, fission fragments and dynamics, taking advantage of the neutron generator and development of gamma-ray spectroscopy techniques at SFU. In particular, it is proposed to deploy the 8p spectrometer in measurements of energy and angular momenta distributions of fission fragments. The program will benefit researchers in nuclear science providing information crucial for validation of state-of-the-art nuclear structure and fission theories while providing excellent training of Highly Qualified Personnel which is of direct benefit to Canada.

低能核物理学最近在对其研究对象的基本理解方面经历了重大范式转变。在轻质和中等质量的原子核中，现在可以在强相互作用的量子色动力学（QCD）理论的启发下提供核结构的从头开始预测，打破了长达数十年的从全局或局部拟合实验数据得出的现象学有效相互作用的统治。在加拿大粒子加速器中心 TRIUMF，加速器和伽马射线探测系统的持续发展允许研究远离稳定的原子核，测试基于接近稳定的数据所开发的理论和理解。  一个引人注目的例子是中子或质子过剩引起的核壳层有序性的变化，它重新排列壳层结构并打破了可观察量的趋势，例如在稳定附近建立的自旋/宇称、质量、结合和激发能。受 QCD 启发，使用二体和三体相互作用的构型相互作用方法可以解决中等质量和重质量原子核的多体核问题，包括那些远离稳定的原子核，而密度泛函理论则将这些相互作用的应用扩展到最重的原子核。当前的理论方法系统地跟踪近似误差，预测趋势和不确定性，从而能够通过与实验数据进行比较来直接测试 QCD 启发的有效相互作用。该计划的长期目标是提高对原子核内核子（质子和中子）之间相互作用的定量理解。 短期目标是通过实验检查核相互作用对质子数 (Z) 和中子数 (N) 之间不对称性的依赖性。特别是，建议利用 TRIUMF 提供的重放射性束执行电磁跃迁率精确测量计划，同时利用西蒙弗雷泽大学 (SFU) 实验基础设施的发展。 TRIUMF 等待执行的实验是测量 55Co 和 55Ni（相对于闭壳 56Ni 的质子和中子空穴核）以及 20Mg（Z=12 处中子最缺乏的同位素）的电磁跃迁速率。还建议利用中子发生器和 SFU 伽马射线光谱技术的发展来研究快中子引起的反应产物以及裂变碎片和动力学。特别是，建议部署 8p 光谱仪来测量裂变碎片的能量和角动量分布。该计划将使核科学研究人员受益，为验证最先进的核结构和裂变理论提供至关重要的信息，同时提供高素质人员的优秀培训，这对加拿大有直接好处。