White Paper on The Majorana Zero-Neutrino Double-Beta Decay Experiment The Majorana Collaboration: Brown University, Providence, RI Institute for Theoretical and Experimental Physics, Moscow, Russia Joint Institute for Nuclear Research, Dubna, Russia Lawrence Berkeley National Laboratory, Berkeley, CA Lawrence Livermore National Laboratory, Livermore, CA Los Alamos National Laboratory, Los Alamos, NM New Mexico State University, Carlsbad, NM Oak Ridge National Laboratory, Oak Ridge, TN Osaka University, Osaka, Japan Pacific Northwest National Laboratory, Richland, WA Queen’s University, Kingston, Canada Triangle Universities Nuclear Laboratory, Durham, NC University of Chicago, Chicago, IL University of South Carolina, Columbia, SC University of Tennessee, Knoxville, TN University of Washington, Seattle, WA November 3, 2003 Approved for public release: LA-UR-2003-7709 and PNNL-14420 The Majorana Zero Neutrino Double-Beta Decay Experiment Abstract The objective of the Majorana Experiment is to study neutrinoless double beta decay (0νββ) with an effective Majorana-neutrino mass sensitivity below 50 meV in order to characterize the Majorana nature of the neutrino, the Majorana mass spectrum, and the absolute mass scale. An experimental study of the neutrino mass scale implied by neutrino oscillation results is now technically within our grasp. This exciting physics goal is best pursued using the well-established technique of searching for 0νββ of 76Ge, augmented with recent advances in signal processing and detector design. The Majorana Experiment will consist of a large mass of 76Ge in the form of high-resolution intrinsic germanium detectors located deep underground within a low-background shielding environment. Observation of a sharp peak at the ββ endpoint will quantify the 0νββ half-life and thus the effective Majorana mass of the electron neutrino. In addition to the modest R&D program, we present here an overview of the entire project in order to help put in perspective the scope, the low level of technical risk, and the readiness of the Collaboration to immediately begin the undertaking. The Majorana Collaboration Brown University, Providence, RI Richard Gaitskell Institute for Theoretical and Experimental Physics, Moscow, Russia Alexander Barabash, Sergey Konovalov, Vladimir Umatov, Igor Vanushin Joint Institute for Nuclear Research, Dubna, Russia Viktor Brudanin, Viatcheslav Egorov, Oleg Kochetov, Viatcheslav Sandukovsky Lawrence Berkeley National Laboratory, Berkeley, CA Yuen-Dat Chan, Paul Fallon, Reyco Henning, Kevin Lesko, Augusto Macchiavelli, Alan Poon Lawrence Livermore National Laboratory, Livermore, CA Kai Vetter Los Alamos National Laboratory, Los Alamos, NM Thedore Ball, Steven Elliott, Victor Gehman, Andrew Hime, Dongming Mei, Geoffrey Mills, Richard Van de Water, Jan Wouters New Mexico State University, Carlsbad NM Joel Webb Oak Ridge National Laboratory, Oak Ridge, TN Thomas V. Cianciolo, Krzysztof P. Rykaczewski, Robert Grzywacz, David Radford, Cyrus Baktash Osaka University, Osaka Japan Hiroyasu Ejiri, Ryuta Hazama, Masaharu Nomachi Pacific Northwest National Laboratory, Richland, WA Craig Aalseth, Dale Anderson, Richard Arthur, Ronald Brodzinski, Glen Dunham, James Ely, Shelece Easterday, Todd Hossbach, David Jordan, Richard Kouzes, Harry Miley, William Pitts, Robert Thompson, Ray Warner Queen’s University, Kingston, Canada Aksel Hallin, Art McDonald Triangle Universities Nuclear Laboratory, Durham, NC Art Champagne, Jeremy Kephart, Ryan Rohm, Konstantin Saburov, Werner Tornow, Albert Young University of Chicago, Chicago, IL Juan Collar University of South Carolina, Columbia, SC Frank Avignone, Richard Creswick, Horatio A. Farach, George King, John M. Palms University of Tennessee, Knoxville TN William Bugg, Yuri Efremenko University of Washington, Seattle, WA Tom Burritt, Peter Doe, Mark Howe, Kareem Kazkaz, Hamish Robertson, John Wilkerson Draft Page ii The Majorana Zero Neutrino Double-Beta Decay Experiment Table of Contents THE MAJORANA ZERO-NEUTRINO DOUBLE-BETA DECAY EXPERIMENT..............................I 1.0 EXECUTIVE SUMMARY............................................................................................................ 1 1.1 PURPOSE OF EXPERIMENT ............................................................................................................ 1 1.2 RESEARCH AND DEVELOPMENT REQUIREMENTS ......................................................................... 1 1.3 ANTICIPATED SENSITIVITY........................................................................................................... 2 1.4 MAJOR REQUIREMENTS ............................................................................................................... 2 1.5 BASIC TIMELINE........................................................................................................................... 2 1.6 CURRENT STATUS ........................................................................................................................ 2 2.0 MAJORANA SCIENCE MOTIVATION.................................................................................... 3 76 2.1 MOTIVATION OF GE 0ν DOUBLE-BETA DECAY ......................................................................... 3 2.2 THE MATRIX ELEMENTS .............................................................................................................. 9 2.3 COMPLETED DOUBLE-BETA DECAY EXPERIMENTS ................................................................... 13 2.4 THE MAJORANA BACKGROUND MODEL .................................................................................... 15 2.5 ULTIMATE SENSITIVITY OF THE MAJORANA EXPERIMENT ......................................................... 16 2.6 OTHER DOUBLE BETA DECAY PROCESSES................................................................................. 18 2.7 OTHER SCIENCE APPLICATIONS OF THE MAJORANA EXPERIMENT............................................. 22 2.8 EDUCATIONAL OUTCOMES......................................................................................................... 32 2.9 OUTREACH PROGRAM ................................................................................................................ 33 3.0 THE MAJORANA EXPERIMENT CONFIGURATION........................................................ 35 3.1 SUMMARY OF THE REFERENCE PLAN ......................................................................................... 35 3.2 OVERVIEW OF THE MAJORANA DESIGN ..................................................................................... 36 3.3 THE BACKGROUND MODEL........................................................................................................ 40 3.4 MONTE CARLO SIMULATIONS .................................................................................................... 65 76 3.5 ISOTOPIC ENRICHMENT OF GE ................................................................................................. 67 3.6 DETECTOR MANUFACTURE ........................................................................................................ 70 3.7 CRYOSTAT AND CRYSTAL PRODUCTION .................................................................................... 78 3.8 SHIELDING ................................................................................................................................. 80 3.9 ELECTRONICS AND DATA ACQUISITION ..................................................................................... 92 3.10 CALIBRATION............................................................................................................................. 99 3.11 ANALYSIS ................................................................................................................................102 3.12 UNDERGROUND FACILITIES...................................................................................................... 107 4 THE ONGOING MAJORANA R&D PROGRAM ..................................................................... 114 4.1 SEGA, MEGA AND MAJORANA .............................................................................................. 114 4.2 SEGA AND MEGA SCIENCE GOALS........................................................................................ 118 5 PROJECT SCHEDULE................................................................................................................. 119 7.0 REFERENCES........................................................................................................................... 123 8.0 APPENDICES ............................................................................................................................ 131 53 77 APPENDIX 3. REPRESENTATION OF THE TABLE OF ISOTOPES FROM MN TO AS................................... 135 APPENDIX 4. ALPHA SIGNALS IN PRIMORDIAL DECAY CHAINS................................................................ 136 Draft Page iii The Majorana Zero Neutrino Double-Beta Decay Experiment 1.0 Executive Summary 1.1 Purpose of Experiment The objective of the Majorana Experiment is to study neutrinoless double beta decay (0νββ) with an effective Majorana-neutrino mass sensitivity below 50 meV in order to characterize the Majorana nature of the neutrino, the Majorana mass spectrum, and the absolute mass scale. An experimental study of the neutrino mass scale implied by neutrino oscillation results is now technically within our grasp. This exciting physics goal is best pursued using the well-established technique