The Majorana Demonstrator Status and Preliminary Results

¹ Oak Ridge National Laboratory, Oak Ridge, TN, USA
² Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, WA, USA
³ Pacific Northwest National Laboratory, Richland, WA, USA
⁴ Department of Physics and Astronomy, University of South Carolina, Columbia, SC, USA
⁵ National Research Center, “Kurchatov Institute” Institute for Theoretical and Experimental Physics, Moscow, Russia
⁶ Department of Physics, University of South Dakota, Vermillion, SC, USA
⁷ Max-Planc-Institute für Physik, München, Germany
⁸ Joint Institute for Nuclear Research, Dubna, Russia
⁹ Triangle Universities Nuclear Laboratory, Durham, NC, USA
¹⁰ Department of Physics, Duke University, Durham, NC, USA
¹¹ Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC, USA
¹² Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
¹³ South Dakota School of Mines and Technology, Rapid City, SD, USA
¹⁴ Los Alamos National Laboratory, Los Alamos, NM, USA
¹⁵ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
¹⁶ Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka, Japan
¹⁷ Department of Physics, Princeton University, Princeton, NJ, USA
¹⁸ Department of Physics, North Carolina State University, Raleigh, NC, USA
¹⁹ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
²⁰ Department of Physics, Black Hills State University, Spearfish, SD, USA
²¹ Physics Department, Tennessee Tech University, Cookeville, TN, USA
²² Department of Physics, Engineering and Astronomy, Queen’s University, Kingston, ON, Canada
²³ Physik Department, Technische Universität, München, Germany

^* Present Address: Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, 28040, Madrid, Spain
^** Alternative address: Department of Nuclear Engineering, University of California, Berkeley, CA, USA

Published online: 16 May 2018

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 Q_ββ. 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.