Thomas Lannen

Date of Award

Fall 2023

Document Type

Open Access Dissertation

Department

Physics and Astronomy

First Advisor

David Tedeschi

Abstract

The Majorana Demonstrator recently concluded its search for neutrinoless double beta decay using an array of up to 40.4kg of germanium detectors, 27kg of which were enriched in 76Ge and housed inside a copper and lead compact shield located at the 4850 foot level in a clean room in the Davis Campus of the Sanford Underground Research Facility (SURF) in Lead, South Dakota. This search proceeded from June 26, 2015 until March 3, 2021 and 64.5 kg yr of enriched active exposure was acquired while achieving a world leading energy resolution of 0.12% FWHM at 2039 keV, one of the lowest background rates in the region of the 0νββ Q-value, 15.7 counts/(FWHM t y), and set a 0νββ half-life limit of T1/2 > 8.3×1025 yrs.

The exposure recovered in the completion of this dissertation resulted in an additional 3.3 kg-yr, which brought the total exposure from 61.9 kg yr up to 65.2 kg-yr, an increase of 5.06%. This increase in exposure enhanced the search for neutrinoless double beta decay by increasing the projected half-life from 7.07×1025 to 7.41×1025 yr an increase of 0.34 × 1025 yr. Furthermore, it is determined that for the Majorana Demonstrator, an event level and run level cut provide near identical levels of utility. In experiments which contain more run selection, an event level cut would be more beneficial. In experiments which contain less run selection, a run level cut would be more beneficial.

Rights

© 2024, Thomas E. Lannen

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