Transfer Reaction Spectroscopy on Neutrinoless Double-Beta Decay Candidate Nuclei

Abstract

A study of the change in neutron occupancies of the A = 116 neutrinoless double-β decay candidate system has been performed. (d, p), (p, d), and (3He, α) reactions were performed on 116Cd and 116Sn targets at theQ3D spectometer at the Maier-Leibnitz Laboratorium in Munich, with states measured up to ∼3 MeV. Transferred angular momenta were determined from the angular distribu- tions of the cross sections. A DWBA analysis was performed to extract the spectroscopic factors of these states, and the MacFarlane-French Sum Rules were applied to extract the valence neutron occupancies. The (d, p) and (p, d) reactions were used to extract the occupancies of the 2s1/2 and 1d orbitals, and the (3He, α) reaction was used to extract the 0g7/2 and 0h 11/2 orbitals. The changes in neutron occupancies between these targets were compared to predictions from QRPA. QRPA is one of the models used to model nuclear matrix elements for neutrinoless double-β decay, and it is hoped that constraining these models to reproduce nucleon occupancies makes predictions of the nuclear matrix elements more consistent. The occupancies were found to be qualitatively consistent with the tin target, but with a more diffuse Fermi surface than predicted by QRPA. However, there was a measured rearrangement of strength between the two targets that was not predicted by the QRPA calculations. A fitting algorithm was designed and used to fit the spectra in this analysis. This algorithm was designed to detect peaks and fit them with minimal user input. This al- gorithm was written in the Python programming language, and used continuous wavelet transforms on spectra split into smaller pieces to detect the peaks.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Sean Freeman (Supervisor) & David Sharp (Supervisor)