P-TYPE POINT CONTACT GERMANIUM DETECTORS AND THEIR APPLICATION IN RARE-EVENT SEARCHES Public Deposited

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  • March 19, 2019
Creator
  • Giovanetti, Graham
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • In the last two decades, experimental results from the direct detection of solar, reactor, and atmospheric neutrinos have provided convincing evidence that neutrinos have mass, the first definitive evidence of physics beyond the Standard Model. The existence of massive neutrinos opens many questions about the neutrino's intrinsic properties, including the absolute mass, the relative hierarchy of the neutrino mass states, and the Majorana or Dirac nature of the neutrino. The MAJORANA DEMONSTRATOR is an array of p-type point contact (PPC) high purity germanium detectors that will search for the neutrinoless double-beta decay of 76-Ge, a process that can only occur if the neutrino is a Majorana particle. PPC detectors have several characteristics that make them well suited for a 76-Ge neutrinoless double-beta decay search, including sub-keV energy thresholds that allow for background rejection based on low-energy x-ray tagging. This feature makes the MAJORANA DEMONSTRATOR sensitive to signals that might be present from processes that are not in the current Standard Model of particle physics. The MAJORANA Low-background Broad Energy Germanium Detector at KURF (MALBEK) is a PPC detector operated at the Kimballton Underground Research Facility (KURF) in Ripplemead, VA. MALBEK was used to test the stability and performance of PPC detectors and study sources of background near the detector energy threshold. It was found that the dominant background below 1 keV in MALBEK data is due to slow surface events, a class of signals originating from interactions that occur near the detector surface. Techniques were developed for identifying surface events and simulating their formation and distribution. These techniques were then applied to 89.5 kg-d of data and searches were performed for signals from weakly interacting massive particles (WIMPs), solar axions, and Pauli exclusion principle violating electron transitions. No evidence of a signal was found. These results are presented in the context of present and future experiments, including the MAJORANA DEMONSTRATOR.
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  • In Copyright
Advisor
  • Engel, Jonathan
  • Radford, David
  • Cecil, Gerald
  • Wilkerson, John
  • Henning, Reyco
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2015
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Place of publication
  • Chapel Hill, NC
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