Recent Results of the Majorana Demonstrator Experiment

TL;DR

The paper reports on the initial results of the Majorana Demonstrator experiment, which searches for neutrinoless double-beta decay in germanium, achieving high energy resolution and setting a new lower limit on the decay's half-life.

Contribution

It presents the first analysis of data from the Majorana Demonstrator, demonstrating improved energy resolution and establishing a new lower limit on neutrinoless double-beta decay half-life.

Findings

Energy resolution of 0.13% at 2039 keV

Background level of 15.4 counts/(FWHM t yr)

Half-life lower limit of 2.7 x 10^{25} years

Abstract

The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay in $^{76}$Ge with two modular arrays of natural and $^{76}$Ge-enriched germanium detectors. It is located at the 4850 level of Sanford Underground Research Facility in Lead, South Dakota, USA, and its total mass of germanium detectors is 44.1 kg, of which 29.7 kg is enriched. The analysis of the first 26 kg-yr of data provides an unprecedented energy resolution of 0.13% in the region of interest at 2039 keV and a background level of 15.4 $\pm$ 2.0 counts/(FWHM t yr). It establishes the lower limit of the half-life of neutrinoless double beta decay as 2.7 10$^{25}$ yr in 76Ge at 90% CL. This analysis will be summarized here with an emphasis on the energy determination.