The Majorana Demonstrator Status and Preliminary Results

C.‐H Yu ,J Gruszko,L Hehn,E Yakushev,M Buuck,J Rager,C Cuesta,C Wiseman,B Shanks,K Vorren,J Myslik,T Bode,T Gilliss,M Shirchenko,I Zhitnikov,G Othman,R L Varner ,K Vetter,W Xu,R Massarczyk,J F Wilkerson ,B.Z Zhu,Pinghan Chu ,S Vasilyev,E W Hoppe ,A López ,M A Howe ,M P Green ,S Mertens,A S Barabash ,A M Suriano ,K J Keeter ,J A Detwiler ,C R Haufe ,S I Alvis ,V.E Guiseppe,C D Christofferson ,F T Avignone ,T S Caldwell ,R Henning,D C Radford ,A W P Poon ,C Dunagan,K Rielage,Yu Efremenko ,Richard T Kouzes ,D J Tedeschi ,M F Kidd ,W Pettus,F E Bertrand ,С И Коновалов ,C J Barton ,G K Giovanetti ,Y.-D Chan,B R White ,H Ejiri,N W Ruof ,S J Meijer ,A L Reine ,I J Arnquist ,V Yumatov,R D Martin ,V Brudanin,S R Elliott ,M Busch,I S Guinn

doi:10.1051/epjconf/201817801006

Abstract

The Majorana Collaboration is using an array of high-purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. Searches for neutrinoless double-beta decay are understood to be the only viable experimental method for testing the Majorana nature of the neutrino. Observation of this decay would imply violation of lepton number, that neutrinos are Majorana in nature, and provide information on the neutrino mass. The Majorana Demonstrator comprises 44.1 kg of p-type point-contact Ge detectors (29.7 kg enriched in 76Ge) surrounded by a low-background shield system. The experiment achieved a high efficiency of converting raw Ge material to detectors and an unprecedented detector energy resolution of 2.5 keV FWHM at Qββ. The Majorana collaboration began taking physics data in 2016. This paper summarizes key construction aspects of the Demonstrator and shows preliminary results from initial data.

Highlights

Neutrinoless double-beta (0νββ) decay experiments play an important role in understanding the nature of neutrinos and their connection with the evolution of the universe
By the fall of 2017, the Demonstrator had collected more than 20 kg yr of data
The first 1.39 kg yr of enriches-Ge data collected with both modules is presented in this paper

Summary

Introduction

Neutrinoless double-beta (0νββ) decay experiments play an important role in understanding the nature of neutrinos and their connection with the evolution of the universe. The observation of 0νββ decay would indicate that lepton number is not conserved – a key ingredient of thermal leptogenesis – and that neutrinos are Majorana particles [1, 2]. Measurements of the 0νββ decay rates would yield information on the absolute neutrino mass. For more comprehensive reviews of 0νββ decays, see Refs. The Majorana Demonstrator is an experiment using enriched- and natural Ge as the detector and source to search for neutrinoless double-beta decay from 76Ge. The primary goal of the Demonstrator is to build a scalable experiment achieving low enough backgrounds to justify the feasibility of a larger-scale experiment. The following sections give a short summary of the design, operation, data analysis and initial results from the Majorana Demonstrator

The Majorana Demonstrator

Data Accumulation and Analysis

Preliminary Results