Speaker
Description
The MAJORANA DEMONSTRATOR was a neutrinoless double-beta decay ($0\nu\beta\beta$) experiment containing ~44 kg of p-type point contact germanium detectors, of which ~30 kg were enriched to 88% in $^{76}$Ge. The DEMONSTRATOR’s low background rate and excellent energy resolution of 2.52 keV at the $0\nu\beta\beta$ Q-value allowed it to set a lower limit of $8.3 \times 10^{25}$ yrs on the $0\nu\beta\beta$ half-life. Through the use of a multi-layer passive shield, radiopure materials, and analysis-based background rejection techniques, the DEMONSTRATOR achieved one of the lowest background rates of all $0\nu\beta\beta$ experiments at the $0\nu\beta\beta$ Q-value, $6.23 \times 10^{-3}$ cnts/(keV kg yr). However, the observed background rate exhibited significant tension with the assay-based projection of $1.17 \times 10^{-3}$ cnts/(keV kg yr). Spectral fits and supplementary background studies indicate that this discrepancy primarily arose from an excess of events from the $^{232}$Th decay chain, which were non-uniformly distributed between the DEMONSTRATOR’s two modules and which did not originate in a near-detector component. This poster presents the results of background model fits, their implications for the next-generation experiment LEGEND-200, and a measurement of the half-life of two-neutrino double-beta decay, incorporating studies of multiple sources of systematic uncertainty.
This material is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.
| Poster prize | Yes |
|---|---|
| Given name | Anna |
| Surname | Reine |
| First affiliation | Indiana University |
| Institutional email | alreine@iu.edu |
| Gender | Female |
| Collaboration (if any) | MAJORANA Collaboration |
