The Majorana Project

TL;DR

The paper discusses the design and planned construction of the Majorana Demonstrator, a low-background, high-purity germanium detector array aimed at detecting neutrinoless double-beta decay to probe neutrino mass in the inverted hierarchy.

Contribution

It introduces a scalable detector design using enriched germanium crystals and ultra-low background materials, demonstrating feasibility with a prototype system for future large-scale experiments.

Findings

Prototype system to evaluate detector technologies

Achievement of ultra-low background levels

Feasibility of scaling to 1-tonne detector mass

Abstract

Building a \BBz experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to \BBz, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the \BBz signal region. The MAJORANA Collaboration proposes a design based on using high-purity enriched Ge-76 crystals deployed in ultra-low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1-tonne size. To demonstrate feasibility, the collaboration plans to construct a prototype system, the MAJORANA DEMONSTRATOR, consisting of 30 kg of 86% enriched \Ge-76 detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to deploy and evaluate two different Ge detector technologies, one based on a p-type configuration and the other on n-type.