Speaker
Description
The nuclides near N=28 are an important testing ground for modern nuclear-structure theory. In addition to the well-known proton and neutron shell closures at calcium-48, doubly magic calcium isotopes have also been proposed at N=32 [1] and N=34 [2]. Fragmentation of single-particle strength also gives insight into basic assumptions of the shell model, such as the nature of the mean field and nucleon correlations [3,4]. Near calcium-48, fragmentation of the fpg orbital strengths is poorly understood and warrants deeper investigation. Furthermore, calcium-48 is a key candidate in neutrinoless double-beta decay searches [5]. Discovery of this rare decay more would have profound implications for the Standard Model, but interpretation of the data will rely heavily on nuclear-structure input.
Nucleon-transfer reactions are an ideal spectroscopic tool to probe the single-particle components of nuclear wavefunctions. After a period of decline, access to research infrastructure required to perform measurements of this kind is undergoing a renaissance. Magnetic spectrometers with high-resolution focal-plane detectors are ideal for studying cases with light-ion beams and stable targets, while solenoidal spectrometers are the preferred option for experiments with rare-ion beams performed in inverse kinematics.
After decades of dedicated use for Accelerator Mass Spectrometry, the Enge Magnetic Spectrometer at the Australian Heavy Ion Accelerator Facility has been restored as a nuclear-spectroscopy device. This presentation will describe the first nuclear-structure experiments performed with the rejuvenated spectrograph, focusing on single-neutron-adding (d,p) studies on N=28 isotones. A complementary study of the single-neutron orbitals at calcium-48, performed in inverse kinematics, will also be discussed.
This work has been supported by the Australian National University Major Equipment Committee (2019), Australian Research Council Grant No. DP210101201 and the International Technology Center Pacific (ITC-PAC) under Contract No. FA520919PA138.
[1] F. Wienholtz et al., Nature 498 346 (2013).
[2] D. Steppenbeck et al., Nature 502 7470 (2013).
[3] T. Otsuka et al., Rev. Mod. Phys. 92 015002 (2020).
[4] A. E. Stuchbery and J. L. Wood, Physics 4 697 (2022).
[5] A. Giuliani and A. Poves, Adv. High Energy Phys. 2012, 857016 (2012).
