The Majorana Neutrinoless Double-Beta Decay Experiment

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1 The Majorana Neutrinoless Double-Beta Decay Experiment A proposed detector to search for neutrinoless double-beta decay Reyco Henning Lawrence Berkeley National Laboratory for the Majorana Collaboration

2 Motivation for 0υββ Search Z A Z+ 2 A + 2e Immediate Implications of Discovery: Neutrino is Majorana (own antiparticle) Total Lepton Number is not conserved Neutrino has mass (known) Well-studied example: Exchange of virtual neutrino 2υββ: Observed 2nd Order Weak Process. Z A Z+ 2 A + 2e + 2ν e QuickTime and a TIFF (LZW) decompressor 5/31/2005 Reyco Henning -- FSU 2

3 Also get: Absolute Neutrino Mass [ 0ν T ] 1 1/ 2 = G 0ν (E 0,Z) m ν 2 M 0ν f (g A / g V ) 2 0ν M GT 2 G 0ν 0ν 0ν M f M GT : Phase Space (Known) : Nuclear Matrix Elements (large uncertainty) g A and g V : Axial-vector and Vector coupling constants m ν : Effective Majorana electron neutrino mass Current neutrino experiments measure mass squared differences: m 2. 0υββ decay can probe absolute neutrino mass scale. 5/31/2005 Reyco Henning -- FSU 3

4 Majorana Reach Mass (mev) ~1 ton Inverted 180 kg ~ years Degenerate Effective ββ 10 Normal 1 U e1 = δm 2 2 = 70 mev sol U e2 = 0.5 δm 2 2 = 2000 mev atm U e3 = Minimum Neutrino Mass (mev) courtesy, S. Elliott 5/31/2005 Reyco Henning -- FSU 4

5 First Recommendation from the Joint Study on the Future of Neutrino Physics -- APS Multidivisional Neutrino Study, Oct We recommend, as a high priority, a phased program of sensitive searches for neutrinoless nuclear double beta decay. The answer to this question is of central importance, not only to our understanding of neutrinos, but also to our understanding of the origin of mass. We are not alone: CANDLES, COBRA, CUORE, DCBA, EXO, GERDA, MOON, NEMO, XMASS Many different approaches. Any discovery REQUIRES verification. 5/31/2005 Reyco Henning -- FSU 5

6 The Majorana Experiment The Majorana experiment first phase is a 180 kg 86% 76 Ge enriched, segmented, HPGe detector array that will search for neutrinoless double-beta decay and dark matter. Key Technologies: 1. Enrichment 2. Materials Selection 3. Underground Manufacturing 4. Pulseshape analysis and segmentation 5. Phased Approach: 180 kg 500 kg 1 ton Proposed Layout (500kg proposal) QuickTime and a 5/31/2005 Reyco Henning -- FSU 6

7 Majorana Collaboration Canada, Japan, Russia, U.S. Brown University Duke University Institute for Theoretical and Experimental Physics Joint Institute for Nuclear Research Lawrence Berkeley National Laboratory Lawrence Livermore National Laboratory Los Alamos National Laboratory North Carolina State University Oak Ridge National Laboratory Osaka University Pacific Northwest National Laboratory Queen s University Triangle Universities Nuclear Laboratory University of Chicago University of South Carolina University of Tennessee University of Washington Pursuing open and valuable technical exchange with Gerda Collaboration. 5/31/2005 Reyco Henning -- FSU 7

8 Detection Principle QuickTime and a Enriched HPGe Diodes -- Detector is Source. Detect Ionization inside HPGE -- Gamma-ray detector technology. Two Neutrino Spectrum Zero Neutrino Spectrum 1% resolution Γ(2 ν) = 100 * Γ(0 ν) Excess at Q = 2038keV courtesy, S. Elliott 2.0 Sum Energy for the Two Electrons (MeV) QuickTime and a TIFF (LZW) decompressor Baseline Detector Concept. Others Being Evaluated 5/31/2005 Reyco Henning -- FSU 8

9 Background Reduction Courtesy: E.E. Haller 68 Ge, 60 Co, U, Th, n, Material Selection Deep Underground Site Underground Manufacturing Time-correlation Shielding Ancient Lead Electroformed Cu Active Muon Veto Active Shield? Neutrons Close-packing PSD/Segmentation Goal: Ge melt Ge seed Ge single crystal Silica crucible An ultra-pure Germanium single crystal is being pulled from a melt contained in a silica crucible at 936 o C. The atmosphere is pure Hydrogen. Heat is supplied by the water cooled radiofrequency (RF) coil surrounding the silica envelope. This bulk crystal growth technique carries the name of it s inventor, Jan Czochralski. E. E. Haller 32 5/31/2005 Reyco Henning -- FSU 9 RF coil

10 Simulation QuickTime and a Joint effort between Gerda/Majorana (MaGe) Professional Software Development Different Designs Potential Backgrounds Background Models 5/31/2005 Reyco Henning -- FSU 10

11 Prototypes and R&D MEGA: 16+2 natural Ge at WIPP Gretina/Greta QuickTime and a TIFF (LZW) decompressor SEGA: Segmented Ge Dark Matter 2νββ TUNL FEL Dark Matter limit Excited state Other Isotopes Pulse Shape Simulation and Analysis Segmentation Studies 5/31/2005 Reyco Henning -- FSU 11

12 Conclusions Strong Physics Motivation for 0υββ Decay Searches. The Majorana Experiment is a Prime Candidate for a 0υββ decay search. Majorana will gain a lot in terms of background reduction from PSD and segmentation. However, the additional wiring and parts required by PSD and segmentation cannot introduce excessive additional backgrounds. 5/31/2005 Reyco Henning -- FSU 12