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Double Beta Decay •Cuore •Majorana •Dingbat

Double Beta Decay •Cuore •Majorana •Dingbat. Only way to distinguish Dirac vs. Majorana, and. (NRC report, NESS). CUORE. Cryogenic Underground Laboratory for Rare Events. J. W. Beeman 1 , E. E. Haller 1,2 , R.J. McDonald 1 , E. B. Norman 1 , A. R. Smith 1 ,

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Double Beta Decay •Cuore •Majorana •Dingbat

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  1. Double Beta Decay •Cuore •Majorana •Dingbat

  2. Only way to distinguish Dirac vs. Majorana, and

  3. (NRC report, NESS)

  4. CUORE Cryogenic Underground Laboratory for Rare Events J. W. Beeman1, E. E. Haller1,2, R.J. McDonald1, E. B. Norman1, A. R. Smith1, A. Giuliani3 , M. Pedretti3, G. Ventura4, M. Balata5, C. Bucci5, C. Pobes5, V. Palmieri6, G. Frossati7, A. de Waard7, C. Brofferio8, S. Capelli8, L. Carbone8, O. Cremonesi8, E. Fiorini8, D. Giugni8, P. Negri8, A. Nucciotti8, M. Pavan8, G. Pessina8, S. Pirro8, E. Previtali8, M. Vanzini8, L. Zanotti8, F. T. Avignone III9, R. J. Creswick9, H. A. Farach9, C. Rosenfeld9, S. Cembrian10, I. G. Irastorza9, A. Morales10 1Lawrence Berkeley National Laboratory,2University of California at Berkeley 3Universita degli Studi dell’Insubria 4Universita’ di Firenze 5Laboratori Nazionali del Gran Sasso 6Laboratori Nazionali di Legnaro 7Leiden University 8Universita’ di Milano-Bicocca 9University of South Carolina 10University of Zaragoza,

  5. Energy absorber TeO2 crystal C  2 nJ/K  1 MeV / 0.1 mK Thermometer NTD Ge-thermistor R  100 MW dR/dT  100 kW/mK Heat sink T  10 mK Thermal coupling G  4 nW / K = 4 pW / mK In real life signal about a factor 2 - 3 smaller Detector concepts • Temperature signal: DT = E/C 0.1 mK for E = 1 MeV • Bias: I  0.1 nA  Joule power  1 pW Temperature rise  0.25 mK • Voltage signal: DV = I  dR/dT DTDV = 1 mV for E = 1 MeV • Signal recovery time: t = C/G  0.5 s • Noise over signal bandwidth (a few Hz): Vrms = 0.2 mV Energy resolution (FWHM):  5 keV at 2500 keV

  6. Properties of 130Te as a DBD emitter 130Te presents several nice features: large phase space, lower background (clean window between full energy and Compton edge of 208Tl photons) • high natural isotopic abundance (I.A. = 33.87 %) • high transition energy (Q = 2528.8 ± 1.3 keV) • encouraging theoretical calculations for 0n-DBD lifetime • already observed with geo-chemical techniques (t 1/2incl = ( 0.7 - 2.7 )  1021 y) <mn>  0.1 eV  t  1026 y 0n-DBD half-life (y) for <mn> = 0.1 eV (different calculations) Comparison with other candidates: Isotopic abundance (%) Transition energy (MeV) 5 1030 40 4 20 1027 3 0 2 1024 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd

  7. Common points: Thermistor: NTD Ge chip glued with epoxy Heat sink: Cu plates, frames and bars Holding method and thermal contact: Teflon elements 1997 2001 • Crystal mass: 340 g - 760 g • Elementary module: 4 detectors • Small amount of Teflon • Crystal surfaces: lapped by us • with radio-pure power • Crystal mass: 340 g • Elementary module: 1 detector • Large amount of Teflon • Crystal surfaces: lapped in China • with 238U-contaminated power Evolution of the detectors Mi DBD - II CUORICINO CUORE Mi DBD - I

  8. 0.3 0.4 0.5 0.6 0.7 0.8 0.1 0.2 CUORICINO sensitivity Detector mass (kg) Running time (y) Isotopic abundance Detector efficiency 1/2 a MT F0n = 4.17  1026  e A b G Atomic mass BKG (counts/keV/kg/y) Energy resolution (keV) Reasonable: b = 0.1 - G = 5 keV Pessimistic: b = 0.3 - G = 10 keV F0n = 8.5  1024(T=1 y) F0n = 3.5  1024(T=1 y) <mn> 0.37 - 0.77 eV <mn> 0.24 - 0.50 eV <mn> (eV) The lower bounds in <mn> range (0.24 eV - 0.37 eV) are obtained with the same matrix elements calculation used in this reference H.V. Klapdor et al. claim: 0.11 - 0.56 eV (0.39 eV c.v.) Mod. Phys. Lett. A 16 (2001) 2409

  9. Crystal Polishing February 2002

  10. Attaching thermistors to TeO2 crystals

  11. LBNL Roles 1999 Development of NTD Ge thermistors 2000 Assisted in construction of MiBeta upgrade 2001 Polishing MiBeta and Cuoricino Crystals 2002 Construction of Cuoricino 2003 Operation of CUORICINO & Submission of CUORE proposal 2004-5 Design clean room for crystal fabrication Produce NTD Ge Thermistors 2006? First delivery of crystals for CUORE 2007? Start of CUORE data taking

  12. CUORE sensitivity Summarizing the BKG contributions: • Bulk contamination is not a problem   0.001 counts/keV/kg/y • Surface contamination is potentially dangerous, but the amount of Cu facing the detector will be reduced by a factor 10 -100 with respect to now   0.01 - 0.001 counts/keV/kg/y Pessimistic estimation: b = 0.01 - G = 5 keV F0n = 1.1  1026 ( T[y ] )1/2 <mn>  66 - 140 meV  ( T[y ] )1/4 Optimistic estimation :b = 0.001 - G = 5 keV F0n =3.6  1026 ( T[y ] )1/2 <mn>  37 - 76 meV  ( T[y ] )1/4

  13. CUORE cost estimation

  14. Collaborators PNNL U of South Carolina TUNL ITEP Dubna NMSU U of Washington Industrial Partners ORTEC Canberra XIA MOXTEK ECP The Majorana Project See http://majorana.pnl.gov for latest project info

  15. e- p+ p+ e- ne n n Majorana Highlights • Neutrinoless double-beta decay of 76Ge potentially measured at 2038.6 keV • Rate of 0n mode determines “Majorana” mass of ne • as low as 0.02-0.07 eV • Requires: • Deep underground location • ~$20M enriched 85% 76Ge • 210 2kg crystals, 12 segments • Advanced signal processing • ~$20M Instrumentation • Special materials (low bkg) • 10 year operation

  16. Pulse-Shape Discrimination and Segmentation for 0nbb-Decay • Major cosmogenic backgrounds (60Co, 68Ge)require multiple depositions to reach ~2 MeV • 0nbb-decay is essentially a single-site process • Pulse-Shape Discrimination (PSD) radial • Single-site depositions create current pulses populating a small area of a well-chosen parameter space. • Multiple-site depositions are linear combinations of single-site current pulse-shapes and populate a larger area of this experimentally verified parameter space. • Segmentation axial and azimuthal • Single-site depositions are nearly always contained in a single detector segment. • Multiple-site depositions usually leave energy in more than one segment, with a probability depending on segment geometry.

  17. Parameter-Space Pulse Shape Discrimination • Sensitive to radial separation of depositions • Self-calibration allows optimal discrimination for each detector • Discriminator can be recalibrated for changing electronic variables • Method is computationally cheap, no computed pulse libraries needed Single site distribution Multiple site distribution

  18. Sensitive to axial and azimuthal separation of depositions Perkin-Elmer design with six azimuthal and two axial contacts has low risk Projected efficacy of this design is excellent with expected backgrounds Detector Segmentation

  19. Moscow-Heidelberg 76Ge Contributed paper B7-2 This Meeting Seeing is believing

  20. Projected SensitivityGround State GIVEN: • Background at 2038 keV = 0.2 cts/keV/kg/y • 68Ge decay 10x reduction • 60Co decay/self shielding/less copper mass 2x reduction • 500 kg 86% 76Ge x 10 years • PSD+Segmentation FOM = 1.6 x 2.4 = 3.8 RESULT: • T0n = 4.0 x 1027 y • <mn> = { 0.020 – 0.068 } eV What is background was ‘zero’? (4.8 counts less) • T0n = 2.0 x 1028 y • <mn> = { 0.009 – 0.031 } eV

  21. The Nygren View Detector R&D: Motivations • Double beta-decay experiments are among highest priority scientific objectives • Experiments which measure “energy only” are vulnerable to backgrounds • Backgrounds have been serious…. • Several nuclei must be studied to reduce systematic errors in interpretation • Several experiments are justifiable Detector R&D - David Nygren

  22. Next Generation • Requirements for next generation “energy-only” experiments are daunting: • Hundreds of kg of stuff are needed! • Backgrounds must be reduced by 10x, x >3 ? • Background limited experiments: t1/4 - bad! • Many years to establish viability • How to establish scaling practicality...

  23. Alternate Idea: Use  Topology •  topology in magnetic field is distinctive • Rejection of ,e backgrounds due to: • Compton scatter, pair production, nuclear decay •  decays, neutron scatters, , wimps,….  Radio-purity issues may be much less important

  24. Topologies - with magnetic field Compton Pair production (“V” shape)  Decay “Dingbat” 

  25. Potentially Stronger Result • Experimental result is an energy spectrum • contains both 2- and 0- decay events, • contains little or no background • Energy resolution expected to be ~1% • Visible 0 peak at endpoint if  is Majorana

  26. Concept: • Develop imaging technique based on: • Image capture by ion drift in insulating liquid • Strong magnetic field to visualize  topology • Track lengths ~1.5 cm (Q of decay, liquid) • Low rate experiment permits slow drift velocity • V = ~ 2 cm/second expected @ 4 kV/cm • Spatial resolution of ~20 m expected @ 5 cm  new kind of TPC-like detector

  27. Many Challenging Issues... • Will topology offer useful discrimination in the presence of multiple scattering ? • Which isotope? • Do isotopes of interest exist in insulating liquid form with acceptable chemistry? • Do ions display unique drift velocities? • Can practical detector modules be made?

  28. Can Magnetic Bending dominate Multiple Scattering? • Multiple scattering degrades topology - • Rough Monte Carlo is encouraging…. • Is overall efficiency high enough to be useful? • How high a magnetic field? • ~2T seems OK, (event radius ~ 3mm) • Algorithmic strategies to discard kinks due to hard scatters must be developed

  29. Which isotope? • 48Ca is ideal • Lowest Z (20), highest Q (4.3 MeV) • Natural abundance very low: 0.2%  problem! • Few insulating liquids with Ca  challenge! • Other possibilities: • 96Zr (2.8% abundance), Z=40 , Q = 3.35 MeV • 82Se (8.7% abundance), Z=34 , Q = 3.0 MeV

  30. Ion Drift in Insulating Liquids • No basic reason why low drift velocity Vd is inappropriate for low rate experiments • Is ion drift velocity Vd single-valued? • Solvation may introduce range of values... • Ion yield may be ~1 ion pair per 200 eV  ~21,000 ion pairs per 0 decay  ~200 ion pairs per measurement along track

  31. Detector Concept • Small signal (200e) drives readout concept  pixellated readout needed to achieve low noise • Low Vd  low bandwidth electronics  low readout noise is possible

  32. Detector Concept…. HV: ~20 kV Basic Module holds ~1 liter of insulating liquid Pixel size is ~100 x 100 m2 Drift  B field  Pixellated readout plane

  33. Summary • Many issues to resolve, but • Potentially very powerful approach • Detector R&D issues not costly to explore • Other next-generation techniques not shown to have adequate background rejection • LBNL should support detector R&D!

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