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The Search for Neutrinoless Double Beta Decay

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Decay and Weak Interaction (A, Z) (A, Z 1) ... GEM. Xe TPC 1. 136Xe (4.2) EXO. Nd foils and tracking chambers. 40. 82Se (2) DCBA. TeO2 bolometers ... – PowerPoint PPT presentation

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Title: The Search for Neutrinoless Double Beta Decay


1
The Search for Neutrinoless Double Beta Decay
  • Tashi Parsons-Moss
  • BNL NCSS 2006

2
ß Decay and Weak Interaction
  • (A, Z) ? (A, Z 1) ß- ??e (1)
  • (A, Z) ? (A, Z - 1) ß ?e (2)
  • (A, Z) e- ? (A, Z - 1) ?e (3)

3
Neutrinos
  • ?e , ?µ , ??
  • 1930 postulated by Pauli
  • 1956 detected by Cowen et al.
  • Oscillations and Mass

4
Double Beta Decay
  • (A, Z) ? (A, Z 2) 2e- 2??
  • (48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 128Te,
    130Te, 150Nd, 238U)
  • (A, Z) ? (A, Z 2) 2e-
  • (A, Z) ? (A, Z 2) 2e- ?0(?0)

5
Possible Mechanisms of 0?ßß decay
  • SUSY particles
  • Leptoquarks
  • Right-Handed weak interaction
  • Light of Heavy Majorana Neutrinos

6
0?ßß Decay and Neutrino Mass
  • 3 Ranges of Mass sensitivity
  • Quasi-Degenerate 100-500 meV
  • Atmospheric neutrino oscillation results
    20-55 meV
  • Solar neutrino oscillation results 2-5 meV


7
Whats the big deal?
  • ? ?? ?
  • Absolute mass scale for neutrinos
  • Leptogenesis
  • Weak Force
  • Grand Unified Theories

8
Challenges
  • Determining the dominant mechanism
  • Uncertainties in nuclear matrix elements
  • Limited resources, expense
  • Background, background, Background!!!
  • 2?ßß peak
  • Cosmic radiation
  • Intrinsic background
  • Shielding and cryostat material

9
Recent 0?ßß results
Isotope Exposure (kmol-y) Background (counts) Half-Life Limit (y) Effective Neutrino Mass Limit (meV)
48Ca 5 x 10-5 0 gt 1.4 x 1022 lt 7200-44700
76Ge 0.467 21 gt 1.9 x 1025 lt 350
76Ge 0.117 3.5 gt 1.6 x 1025 lt 330 - 1350
76Ge 0.943 61 1.2 x 1025 440
82Se 7 x 10-5 0 gt 2.7 x 1022 (68) lt 5000
100Mo 5 x 10-4 4 gt 5.5 x 1022 lt 2100
116Cd 1 x 10-3 14 gt 1.7 x 1023 lt 1700
128Te Geochemical NA gt 7.7 x 1024 lt 1100-1500
130Te 0.025 5 gt 5.5 x 1023 lt 370 - 1900
136Xe 7 x 10-3 16 gt 4.4 x 1023 lt 1800-5200
150Nd 6 x 10-5 0 gt 1.2 x 1021 lt 3000
10
Recent claim of 0?ßß detection
11
Heidelberg-Moscow
  • 71.7 Kg-y data
  • Controversial Results
  • Increased interest in quasi-degenerate 76Ge
    experiments

12
0?ßß Proposals
Collaboration Isotope (kmol) Anticipated Background (counts/y) Detector Description
CAMEO 116Cd (2) Few CdWO4 crystals in liquid scintillator
CANDLES 48Ca (0.04) CaF2 crystals in liquid scintillator
COBRA 130Te CdTe semiconductors
CUORE 130Te (1.4) 60 TeO2 bolometers
DCBA 82Se (2) 40 Nd foils and tracking chambers
EXO 136Xe (4.2) lt 1 Xe TPC
GEM 76Ge (11) 0.8 Ge detectors in LN
GENIUS 76Ge (8.8) 0.6 Ge detectors in LN
GSO 160Gd (1.7) Gd2SiO5 crystals in liquid scintillator
Majorana 76Ge (3.5) 1 Segmented Ge detectors
MOON 100Mo (2.5) 8 Mo foils and plastic scintillator
MPI bare Ge 76Ge (8.8) Ge detectors in LN
Nano-crystals 100 kmol Suspended nanoparticles
Super-NEMO 82Se (0.6) 1 Foils with tracking
Xe 136Xe (6.3) 118 Xe dissolved in liquid scintillator
XMASS 136Xe (6.1) Liquid Xe
13
GENIUS (Germanium Nitrogen Underground Setup)
  • Assumes limiting background on HM from external
    sources
  • Array of 2.5 Kg p-type 86 enriched Ge crystals
    naked in LN2

14
Majorana
  • Assumes 68Ge within Ge detectors was limiting
    background in IGEX
  • 210 86 enriched, segmented n-type Ge crystals in
    ultra-pure electroformed Cu cryostats

15
Majorana
16
MOON (Mo Observatory of Neutrinos)
  • Uses unique nuclear structure of 100Mo to combine
    0?ßß search and solar neutrino experiment
  • Modules of plastic fiber scintillators with thin
    layers Mo

17
MOON
18
Acknowledgements
  • I would like to thank Richard Ferrieri and all of
    the TAs, professors, students and supporters of
    the BNL Nuclear and Radiochemistry Summer School
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