The Majorana Demonstrator: Progress towards showing the feasibility of a tonne–scale 76Ge neutrinoless double–beta decay experiment

P Finnerty ,N Fields ,R Henning ,J I Collar ,V Egorov ,A Schubert ,Y V Efremenko ,W Tornow ,J E Fast ,J F Wilkerson ,R G H Robertson ,A Knecht ,M Amman ,Michael L Miller ,Nicole Overman ,M Nomachi ,K J Keeter ,J H Merriman ,D G Phillips ,E Yakushev ,J Strain ,M Shirchenko ,K Rielage ,R Hazama ,V E Guiseppe ,O Kochetov ,J L Orrell ,С И Коновалов ,M Boswell ,A W P Poon ,Richard T Kouzes ,M Busch ,S Howard ,G Perumpilly ,H Ejiri ,M G Marino ,P.n Luke ,M Ronquest ,J A Detwiler ,A R Young ,K J Snavely ,K Vetter ,A Galindo‐Uribarri ,K Gusey ,J Esterline ,T Shima ,C D Christofferson ,A S Barabash ,V Brudanin ,V M Gehman ,R D Martin ,D Steele ,S R Elliott ,M A Howe ,Y-D Chan ,E Aguayo ,Paul Barton ,F Bertrand ,D C Radford ,J R Beene ,C H Yu ,D C Combs ,K Vorren ,M F Kidd ,R Cooper ,R L Varner ,Mark Horton ,L Mizouni ,A L Hallin ,F M Fraenkle ,Rob Johnson ,E W Hoppe ,J Leon ,B D Laferriere ,M P Green,V Timkin ,S Macmullin ,F T Avignone ,G K Giovanetti ,L E Leviner ,H Yaver ,P J Doe ,J C Loach ,V Yumatov

doi:10.1088/1742-6596/485/1/012042

Abstract

The Majorana Demonstrator will search for the neutrinoless double–beta decay (0vββ) of the 76Ge isotope with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own anti–particle, demonstrate that lepton number is not conserved, and provide information on the absolute mass–scale of the neutrino. The Demonstrator is being assembled at the 4850 foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be contained in a low–background environment and surrounded by passive and active shielding. The goals for the Demonstrator are: demonstrating a background rate less than 3 t−1 y−1 in the 4 keV region of interest (ROI) surrounding the 2039 keV 76Ge endpoint energy; establishing the technology required to build a tonne–scale germanium based double–beta decay experiment; testing the recent claim of observation of 0vββ [1]; and performing a direct search for light WIMPs (3-10 GeV/c2).

Highlights

The Majorana collaboration [2, 3, 4] will search for the neutrinoless double-beta decay (0νββ) of 76Ge
Mitigation Techniques One of the technical goals of the Demonstrator is to show that a 1 t−1 y−1 region of interest (ROI)−1 background rate is achievable for a tonne-scale experiment; this scales to 3 t−1 y−1 ROI−1 background rate for the Demonstrator, which is ∼100 times lower than previous Ge experiments
The low-thresholds and excellent energy resolution of p-type point contact (PPC) detectors allow for a single-site timecorrelation (SSTC) cut, which looks forward and backward in time from the current event in the ROI to search for signatures of parent or daughter isotopes [14, 15]

Summary

21 Alternate Address

17Research Center for Nuclear Physics and Department of Physics, Osaka University, Ibaraki, Osaka, Japan 18Department of Physics, University of South Dakota, Vermillion, SD, USA 19Centre for Particle Physics, University of Alberta, Edmonton, AB, Canada 20Department of Physics, Black Hills State University, Spearfish, SD, USA

Introduction

Background

Findings

Demonstrator Implementation