1 / 23

Majorana

Majorana. Majorana: Searching for neutrinoless double beta decay in 76 Ge Henning Olling Back North Carolina State University Triangle Universities Nuclear Laboratory For the Majorana Collaboration. The Majorana Collaboration. Brown University, Providence, Rhode Island

jeffreyl
Download Presentation

Majorana

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Majorana Majorana: Searching for neutrinoless double beta decay in 76Ge Henning Olling Back North Carolina State University Triangle Universities Nuclear Laboratory For the Majorana Collaboration

  2. The Majorana Collaboration • Brown University, Providence, Rhode Island • Michael Attisha,Rick Gaitskell, John-Paul Thompson • Institute for Theoretical and Experimental Physics, Moscow, Russia • Alexander Barabash, Sergey Konovalov, Igor Vanushin, Vladimir Yumatov • Joint Institute for Nuclear Research, Dubna, Russia • Viktor Brudanin, Slava Egorov, K. Gusey,S. Katulina, OlegKochetov, M. Shirchenko, Yu. Shitov, V. Timkin, T. Vvlov, E. Yakushev, Yu. Yurkowski • Lawrence Berkeley National Laboratory, Berkeley, California • Yuen-Dat Chan, Mario Cromaz, Paul Fallon, Brian Fujikawa, Reyco Henning, Donna Hurley, Kevin Lesko, Paul Luke, Augusto O. Macchiavelli, Akbar Mokhtarani, Alan Poon, Gersende Prior, Al Smith, Craig Tull • Lawrence Livermore National Laboratory, Livermore, California • Dave Campbell, Kai Vetter • Los Alamos National Laboratory, Los Alamos, New Mexico • Mark Boulay, Steven Elliott, Gerry Garvey, Victor M. Gehman, Andrew Green, Andrew Hime, Bill Louis, Gordon McGregor, Dongming Mei, Geoffrey Mills, Kieth Rielage, Larry Rodriguez, Richard Schirato, Laura Stonehill, Richard Van de Water, Hywel White, Jan Wouters • Oak Ridge National Laboratory, Oak Ridge, Tennessee • Cyrus Baktash, Jim Beene, Fred Bertrand, Thomas V. Cianciolo, David Radford, Krzysztof Rykaczewski, Chang-Hong Yu Osaka University, Osaka, Japan Hiroyasu Ejiri, Ryuta Hazama, Hidehito Nakamura, Masaharu Nomachi Pacific Northwest National Laboratory, Richland, Washington Craig Aalseth, Ronald Brodzinski, James Ely, Tom Farmer, Jim Fast, Eric Hoppe, Brian Hyronimus, David Jordan, Jeremy Kephart,Richard T. Kouzes, Harry Miley, John Orrell, Jim Reeves, Robert Runkle, Bob Schenter, John Smart, Ray Warner, Glen Warren Queen's University, Kingston, Ontario Fraser Duncan, Aksel Hallin, Art McDonald Triangle Universities Nuclear Laboratory, Durham, North Carolina and Physics Departments at Duke University and North Carolina State University Henning Back, James Esterline, Mary Kidd, Werner Tornow, Albert Young University of Chicago, Chicago, Illinois Juan Collar University of South Carolina, Columbia, South Carolina Frank Avignone, Richard Creswick, Horatio A. Farach, Todd Hossbach, George King University of Tennessee, Knoxville, Tennessee William Bugg, Tom Handler, Yuri Efremenko, Brandon White University of Washington, Seattle, Washington John Amsbaugh, Jason Detwiler, Peter J. Doe, Alejandro Garcia, Mark Howe, Rob Johnson, Kareem Kazkaz, Michael Marino, Sean McGee, R. G. Hamish Robertson, Alexis Schubert,Brent VanDevender,John F. Wilkerson Note: Red text indicates students

  3. 100Tc 100Mo ββ 100Ru γ 590.8 keV γ 539.6 keV Two Neutrino Double beta decay • Half-life on the order of 1019 years (age of Universe ~ 1010 y) • Isotopes – 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 110Pd, 116Cd, 124Sn, 130Te, 136Xe, 150Nd, etc. Double beta decay to excited states measured at TUNL

  4. What if ν = anti-ν ? Half-life of at least 1025 years Endpoint for 76Ge ~ 2039 keV _ νR Mm νL Neutrinoless double beta decay Majorana mass

  5. Double beta decay spectrum

  6. By just observing neutrinoless double beta decay Total lepton number not conserved Neutrinos are Majorana particles By measuring decay rate we get an effective majorana mass of neutrino G0νis a calculable phase space factor |M0 ν| is a VERY hard to calculate nuclear matrix element. Determination of an effective majorana neutrino mass can tell us something about mass hierarchy Results of a positive measurement (S. Elliot)

  7. Ge as source & detector. Elemental Ge maximizes the source-to-total mass ratio. Intrinsic high-purity Ge diodes. Favorable nuclear matrix element |M0|=2.4 [Rod05]. Reasonably slow 2 rate( = 1.4  1021 y). Demonstrated ability to enrich from 7.44% to 86%. Excellent energy resolution — 0.16% at 2.039 MeV, 4 keV ROI Powerful background rejection. Segmentation, granularity, timing, pulse shape discrimination Best limits on 0- decay used Ge (IGEX & Heidelberg-Moscow)  > 1.9  1025 y (90%CL) Well-understood technologies Commercial Ge diodes Large Ge arrays (GRETINA, Gammasphere) The Majorana 76Ge Experiment 76Ge offers an excellent combination of capabilities and sensitivities. [Rod05] V. A. Rodin, A. Faessler, F. Simkovic, and P. Vogel (2005), nucl-th/0503063.

  8. The Majorana Experiment Overview • Reference Design • Based on 60 kg modules, each containing 57 segmented, n-type, 86% enriched 76Ge crystals • Scalable, with independent, ultra-clean, electroformed Cu cryostat modules • Enclosed in a low-background passive shield and active veto • Located deep underground (4500 - 6000 mwe) • Background Specification in the 0peak region of interest (4 keV at 2039 keV) ~ 1 count/t-y (after background cuts) • Expected Sensitivity to 0(for two modules and 4.5 years, or 0.46 t-y of 76Ge exposure) T1/2 >= 5.5 x 1026 y (90% CL) <m> < 100 meV (90% CL) ([Rod05] RQRPA matrix elements) or a 10-20% measurement assuming a 400 meV value.

  9. Cap Tube (0.007” wall) Ge (62mm x 70 mm) Tray (Plastic, Si, etc) The Majorana Modular Approach • 57 crystal module: 60 kg of Ge per module • Conventional vacuum cryostat made with electroformed Cu. • Three-crystal stacks are individually removable. Vacuum Jacket Cold Finger

  10. Background mitigation • Sensitivity to 0 decay is ultimately limited by S-to-B. • Goal: ~ 150 times lower background (after analysis cuts) than previous 76Ge experiments. • Approach – detector unspecific • Shielding the detector from external natural and cosmogenic sources • Ultra-pure materials used in proximity to the crystals • electroformed Cu • development of ultra-senstive ICPMS methods for materials assay • Approach – detector specific • Optimizing the detector energy resolution • Granularity • Time correlation analysis • Pulse shape analysis • Segmentation

  11. Cosmogenic isotopes 68Ge in crystals 60Co in copper Neutrons produced in rock or shield can produce other radio isotopes in cryostat or copper Cosmic rays [Mei05] [Mei05] D.-M. Mei and A. Hime, Physical Review D 73, 053004 (2005), astro-ph/0512125.

  12. The Majorana Shield - Conceptual Design • Inner liner: 10 cm ultra-low background e-formed Cu • Bulk shield: 40 cm Pb, two detector modules shown • Active 4 veto detector • Outer sheath: 30 cm polyethylene layer

  13. Semiconductor-grade acids Copper sulfate purified by recrystallization Baths circulated with continuous microfiltration to remove oxides and precipitates Continuous barium scavenge removes radium Cover gas in plating tanks reduces oxide formation Periodic surface machining during production minimizes dendritic growth H2O2 cleaning, citric acid passivation Electroforming copper C C A A B B CuSO4 Electroforming copper - key elements 232Th < 1Bq/kg

  14. New test lab: class 2000 (frequently class 1300) Improved bath chemistry requires less surface finishing (less machining and handling) Improved starting stock quality and handling Electroforming improvements 2006 N2 sparge gas flow control Particulate filtration and Radium scavenge Off-gas vent Front view Side view Inner bath containment & Cu bus Cu sulfate bath Programmable power supply

  15. Keeping crystals clean • Some radioactive isotopes are cosmogenically produced • 60Co – minimize surface time after zone refined • 68Ge – minimize surface time from Russia Shipping Concept: 2m cube Storage Concept: 4m cube

  16. g (“High” Energy) 0nbb g g 60Co g (“Low” Energy) Event ID - segmentation • Gammas travel further in Ge than betas • Gammas can scatter multiple times • Betas appear as “single sited” events • Segmentation can help identify multiple scatters

  17. Reference Plan: 1.1 kg detector 62 mm diameter/70 cm high 2 x 3 segmented n-type detector Considerations underway: Monte Carlo design R&D Alternatives R&D Costing analysis Surface preparations Cabling and small parts Crystal Segmentation

  18. Pulse shape analysis (PSA) • Multiple scatters in one segment produce broad pulses • Studying pulse shapes can further reduce background Data from LANL clover 228Ac 208Tl DEP

  19. Granularity • Granularity cut: Simultaneous signals in two detectors cannot be 0nbb • Requires tightly packed Ge • Successful against: • 208Tl and 214Bi • Supports/small parts (~5x) • Cryostat/shield (~2x) • Some neutrons • Muons (~10x) ~ 40 cm Granularity is intrinsic to the design and a powerful background suppressor.

  20. Sensitivity with respect to mass Although we will confirm/refute the KKDC claim early on, it is not driving physics goal. 0.46 t-y

  21. Majorana Sensitivity & Backgrounds

  22. Majorana Summary • The 76Ge modular design is based on demonstrated technology, that is scalable to larger mass • The collaboration has extensive experience in -decay experiments and fielding low-background, large neutrino detectors. • Concentrating on developing the first 60 kg module, with options to later add additional modules • Received a favorable review and recommendation from NuSAG in Fall 2005 • In November 2005 approved by DOE NP to proceed with R&D as well as with Conceptual Design activities (Critical Decision 0) • In November 2006 DOE review of proposal With 460 kg-y exposure Majorana can reach a lifetime limit of 5.5 x 1026 y (90% CL) corresponding to a neutrino mass of 100 meV or perform a 10% precision measurement assuming a 400 meV value

  23. Neutrino Scientific Assessment Group - Fall 05 Recommendation:The Neutrino Scientific Assessment Group recommends that the highest priority for the first phase of a neutrino-less double beta decay program is to support research in two or more neutrino-less double beta decay experiments to explore the region of degenerate neutrino masses (‹m›> 100 meV). The knowledge gained and the technology developed in the first phase should then be used in a second phase to extend the exploration into the inverted hierarchy region of neutrino masses (‹m› > 10−20 meV) with a single experiment. Majorana: The excellent background rejection achieved from superior energy resolution in past 76Ge experiments must be extended using new techniques. The panel notes with interest the communication between the Majorana and GERDA 76Ge experiments which are pursuing different background suppression strategies. The panel supports an experiment of smaller scope than Majorana-180 that will allow verification of the projected performance and achieve scientifically interesting physics sensitivity, including confirmation or refutation of the claimed 76Ge signal. A larger 76Ge experiment is a good candidate for a larger international collaboration due to the high cost of the enriched isotope.

More Related