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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=717893
• 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 8 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的范式转变。在轻和中等质量的原子核中，现在可以提供受强相互作用的量子色动力学（QCD）理论启发的原子核结构的从头计算预测，打破了数十年来从全球或局部拟合实验数据得出的唯象有效相互作用的统治。在加拿大的TRIUMF粒子加速器中心，加速器和伽马射线探测系统的持续发展使人们能够研究远离稳定状态的原子核，检验根据接近稳定状态所获得的数据而形成的理论和认识。 一个突出的例子是由中子或质子过剩引起的核壳层有序的变化，它重新排列了壳层结构，打破了自旋/宇称、质量、结合和激发能等接近稳定的观测值的趋势。组态相互作用方法使用二体和三体相互作用的启发QCD允许解决多体核问题的中，重质量的核，包括那些远离稳定，而密度泛函理论提供了一个扩展的应用程序，这些相互作用的最重的核。目前的理论方法系统地跟踪近似误差，预测趋势与不确定性，从而使直接测试QCD激发的有效相互作用，通过比较实验数据。 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研究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，它建议执行一个程序的电磁跃迁率的精确测量使用重放射性光束提供的TRIUMF，同时利用西蒙弗雷泽大学（SFU）的实验基础设施的发展。在TRIUMF等待执行的实验是测量55 Co和55 Ni的电磁跃迁率，它们是相对于封闭壳层56 Ni的质子和中子空穴核，以及20 Mg，Z=12时最缺中子的同位素。还建议利用SFU的中子发生器和伽马射线光谱技术的发展，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，它建议部署在裂变碎片的能量和角动量分布的测量8光谱仪。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关键信息，同时提供对加拿大直接受益的高素质人员的良好培训。