High-precision spectroscopy and exotic nuclear structure

这项拨款申请支持我的团队--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--进行与三个主要主题相一致的研究：在TRIUMF-ISAC设施开发用于两个地方的中子探测的下降探测器 与加速束的核反应，以及β延迟中子 测量、核结构研究以了解核中集体的起源和性质，以及核的核结构研究对于基本对称性测试和探索超越标准模型的物理非常重要。 Descant是一个价值200万美元的CFI项目，是一个由70个重氢苯液体闪烁体探测器组成的阵列，可与Griffin伽马射线能谱仪结合使用，以利用TRIUMF通过开发Ariel设施提供的新能力，该设施将提供密集的丰中子核光束，其中许多将具有大量的贝塔延迟中子发射分支。当与TIGRESS伽马射线能谱仪连接时，它为加速的富中子束引起的反应提供了一个灵敏的通道选择器。 我们的核结构研究探索了集体的发展，主要是在CD区域。将核寿命测量的结果与非常高的统计贝塔衰变测量结果相结合，可以详细绘制集体图。Cd同位素被认为是球面振动运动的一些最好的例子，但我们最近的工作对此提出了质疑。我们正在通过高统计量的β衰变实验，将我们的研究扩展到Z=50以上的区域，即Te和Xe同位素。我们的研究包括在德国Garching的迈尔-莱布尼茨实验室使用Q3D磁谱仪进行的核子转移和非弹性散射反应的研究。 除了上述调查外，我的小组还一直在积极开展核结构研究，以支持基本对称性测试。利用Q3D光谱仪，对超允许费米β衰变中重要的同位旋对称性破缺修正项所依据的结构计算的准确性进行了实验，该修正项用于推导CKM矩阵的VUD元素。 一项主要的新举措是对199汞附近的原子核进行调查，目的是限制199汞希夫矩的模型。对于原子电偶极矩的存在，最严格的限制是199汞。然而，由于缺乏光谱数据，尤其是E_1、E_2和E_3强度分布的缺乏，199Hg希夫矩的模型一直受到阻碍。在我们计划的第一阶段，我们正在研究198,200汞通过非弹性散射(d，d‘)反应和单中子转移到199汞。这些研究将扩展到通过(n，n‘伽马)和(p，p’伽马)反应进行伽马射线测量。

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 both nuclear reactions with accelerated beams, and beta-delayed neutron measurements, 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.