High-precision spectroscopy and exotic nuclear structure

这项资助申请支持我的团队——目前由1名研究助理、4名博士、3名硕士和3名本科生组成——他们的研究与三个主要主题相一致；在TRIUMF-ISAC设施开发DESCANT探测器，用于在加速束核反应和β -延迟中子测量中进行中子探测，进行核结构研究，以了解原子核集体的起源和性质，以及对基本对称性测试和寻找超越标准模型的物理非常重要的核结构研究。DESCANT是一个价值200万美元的CFI项目，是一个由70个氘化苯液体闪烁体探测器组成的阵列，可以与GRIFFIN伽马射线光谱仪结合使用，利用TRIUMF提供的新能力，开发ARIEL设施，提供富含中子的强束，其中许多将具有大量的β -延迟中子发射分支。当与TIGRESS伽马射线光谱仪耦合时，它为加速富中子束引起的反应提供了灵敏的通道选择器。我们的核结构研究探讨了集体的发展，主要是在Cd地区。将核寿命的测量结果与高统计量的β衰变测量结果相结合，可以详细地绘制集体图。Cd同位素被认为是球形振动运动的最佳例子之一，但我们最近的工作对这一点提出了质疑。我们正在将我们的研究扩展到Z=50以上的区域，即Te和Xe同位素，并进行高统计的β衰变实验。我们的研究包括在德国Garching的Maier-Leibnitz实验室用Q3D磁谱仪进行的核子转移和非弹性散射反应的研究。除了上述研究之外，我的小组也一直在积极地进行核结构研究，以支持基本的对称性测试。利用Q3D光谱仪，进行了实验，以测试在超允许费米衰变中重要的同位旋对称破缺校正项（用于推导CKM矩阵的Vud元素）基础上的结构计算的准确性。一项重要的新举措是对199Hg附近的原子核进行研究，目的是建立199Hg希夫矩的约束模型。原子电偶极矩存在的最严格限制是199Hg。然而，由于缺乏光谱数据，特别是E1、E2和E3强度分布的数据，199Hg的希夫矩模型一直受到阻碍。在我们计划的第一阶段，我们通过非弹性散射（d,d'）反应和单中子转移到199Hg来研究198,200Hg。这些研究将通过（n,n' γ）和（p,p' γ）反应扩展到伽马射线测量。

This grant application support my group - currently consisting of 1 Research Associate, 4 PhD, 3 MSc, and 3 undergraduate students - in their research that is aligned along three major themes; development of the DESCANT detector at the TRIUMF-ISAC facility for neutron detection in bothnuclear reactions with accelerated beams, and beta-delayed neutronmeasurements, nuclear structure studies to understand the origin and nature of collectivity in nuclei, and nuclear structure studies of nuclei important for fundamental symmetry tests and searches for physics beyond the Standard Model. DESCANT, a $2M CFI project, is an array of 70 deuterated benzene liquid scintillator detectors that can be used, in combination with the GRIFFIN gamma-ray spectrometer to take advantage of the new capabilities offered by TRIUMF with the development of the ARIEL facility that will provide intense beams of neutron-rich nuclei, many of which will have substantial beta-delayed neutron emission branches. When coupled to the TIGRESS gamma-ray spectrometer, it offers a sensitive channel selector for reactions induced by accelerated neutron rich beams. Our nuclear structure studies have probed the development of collectivity, mainly in the Cd region. Combining results from measurements of nuclear lifetimes with very-high-statistics beta-decay measurements enables a detailed mapping of collectivity. The Cd isotopes were believed to be some of the best examples of spherical vibrational motion, but our recent work has called this into question. We are extending our research into the region above Z=50, namely the Te and Xe isotopes, with high-statistics beta-decay experiments. Our investigations include studies with nucleon transfer and inelastic scattering reactions performed with the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory in Garching, Germany.In addition to the above investigations, my group has also been actively pursuing nuclear structure studies to support fundamental symmetry tests. Using the Q3D spectrograph, experiments were performed to test the accuracy of the structure calculations underlying the isospin symmetry breaking correction terms important in superallowed Fermi beta decay - used to derive the Vud element of the CKM matrix. A major new initiative undertaken is the investigation of nuclei in the vicinity of 199Hg with the aim of constraining models of the 199Hg Schiff moment. The most stringent limit on the existence of an atomic electric-dipole moment is that for 199Hg. Models of the Schiff moment of 199Hg have been hampered, however, by the lack of spectroscopic data, most notably of the E1, E2, and E3 strength distributions. In the first phase of our program, we are studying 198,200Hg via the inelastic scattering (d,d') reactions and single-neutron transfer into 199Hg. These studies will be extended to gamma-ray measurements via the (n,n'gamma) and (p,p'gamma) reactions.