Document Type

Dissertation

Date of Award

2022

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Wenqin Xu

Abstract

Neutrinoless double-beta decay (0νββ) is a hypothetical nuclear transition which, if observed, would prove that neutrinos are Majorana particles. In addition, the decay rate could provide an effective neutrino mass scale. The decay violates lepton number conservation and could offer a potential path to explain the matter-antimatter asymmetry in the universe via leptogenesis. However, the experimental observation of this decay is very challenging and would require excellent energy resolution of detectors, low background levels, and high exposure. The MAJORANA DEMONSTRATOR experiment searches for this decay in 76Ge using P-type Point Contact (PPC) High Purity Germanium (HPGe) detectors. In addition, the DEMONSTRATOR is probing a broad range of physics, including both Standard Model (SM) physics and Beyond the Standard Model (BSM) physics, thanks to the experiment's excellent energy performance, low analysis energy threshold, and low background. This dissertation will begin with an overview of neutrinos and neutrinoless double-beta decay physics. It will then briefly outline the MAJORANA DEMONSTRATOR experiment and its result on 0νββ search. The DEMONSTRATOR has achieved the best-in-field energy resolution, which is the result of intrinsic properties of detectors and analysis efforts. A brief description of the energy calibration procedure and the energy systematic study of DEMONSTRATOR will be presented. Then, the dissertation will describe an experimental study of 13C(α,n)16O reactions in MAJORANA's calibration data. The findings and impacts in low-background experiments will be presented. Finally, it will describe the machine learning approach of analyzing waveforms to discriminate signal-like and background-like events for 0νββ searches.

Subject Categories

Other Physics

Keywords

Neutrinoless

Number of Pages

149

Publisher

University of South Dakota

Included in

Other Physics Commons

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