The MAJORANA DEMONSTRATOR: Progress towards showing the feasibility of a tonne-scale 76Ge neutrinoless double-beta decay experiment

TL;DR

The paper reports on progress in developing the MAJORANA DEMONSTRATOR, a low-background germanium detector array, to demonstrate the feasibility of a large-scale neutrinoless double-beta decay experiment and explore related physics.

Contribution

It presents advancements in detector technology and background reduction crucial for scaling up to a tonne-scale experiment.

Findings

Achieved background rate below 3 events per tonne-year in the ROI.

Demonstrated technology for a large-scale germanium detector array.

Performed initial searches for neutrinoless double-beta decay and light WIMPs.

Abstract

The MAJORANA DEMONSTRATOR will search for the neutrinoless double-beta decay of the 76Ge isotope with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own anti-particle, demonstrate that lepton number is not conserved, and provide information on the absolute mass-scale of the neutrino. The DEMONSTRATOR is being assembled at the 4850 foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be contained in a low-background environment and surrounded by passive and active shielding. The goals for the DEMONSTRATOR are: demonstrating a background rate less than 3 t$^{-1}$ y$^{-1}$ in the 4 keV region of interest (ROI) surrounding the 2039 keV 76Ge endpoint energy; establishing the technology required to build a tonne-scale germanium based double-beta decay experiment; testing the recent claim of observation of neutrinoless double-beta decay [H. V. Klapdor-Kleingrothaus and I. V. Krivosheina, Mod. Phys. Lett. A21, 1547 (2006)]; and performing a direct search for light WIMPs (3-10 GeV).