Initial Results from the MAJORANA DEMONSTRATOR

TL;DR

The paper reports initial results from the MAJORANA DEMONSTRATOR, a Ge detector array designed to search for neutrinoless double-beta decay, aiming to establish background levels and scalability for future large-scale experiments.

Contribution

It presents the first physics data and commissioning results of the MAJORANA DEMONSTRATOR, demonstrating progress towards a scalable, low-background Ge-based neutrinoless double-beta decay experiment.

Findings

Initial detector module commissioning results

Background levels suitable for future scaling

Progress towards full detector array assembly

Abstract

Neutrinoless double-beta decay searches seek to determine the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The {\sc Majorana} Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in $^{76}$Ge. The {\sc Majorana Demonstrator} is composed of 44.8~kg (29.7 kg enriched in $^{76}$Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals of the {\sc Demonstrator} are to establish the required background and scalability of a Ge-based, next-generation, tonne-scale experiment. Following a commissioning run that began in 2015, the first detector module started physics data production in early 2016. We will discuss initial results of the Module 1 commissioning and first physics run, as well as the status and potential physics reach of the full {\sc Majorana Demonstrator} experiment. The collaboration plans to complete the assembly of the second detector module by mid-2016 to begin full data production with the entire array.