The Search for Neutrinoless Double Beta Decay
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Transcript of The Search for Neutrinoless Double Beta Decay
The Search for Neutrinoless Double Beta Decay
Tashi Parsons-Moss
BNL NCSS 2006
β Decay and Weak Interaction
(A, Z) (A, Z + 1) + β- + e (1)
(A, Z) (A, Z - 1) + β+ + e (2)
(A, Z) + e- (A, Z - 1) + e (3)
Neutrinos
e , µ , 1930 – postulated by
Pauli 1956 – detected by
Cowen et al. Oscillations and Mass
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)
Possible Mechanisms of 0ββ decay
SUSY particles
Leptoquarks
Right-Handed weak
interaction
Light of Heavy
Majorana Neutrinos
0ββ 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
What’s the big deal?
= ?
Absolute mass scale for
neutrinos
Leptogenesis
Weak Force
Grand Unified Theories
Challenges
Determining the dominant mechanism Uncertainties in nuclear matrix elements Limited resources, expense Background, background, Background!!!
2ββ peak Cosmic radiation Intrinsic background Shielding and cryostat material
Recent 0ββ results
Isotope Exposure (kmol-y) Background (counts)
Half-Life Limit (y) Effective Neutrino Mass Limit (meV)
48Ca 5 x 10-5 0 > 1.4 x 1022 < 7200-44700
76Ge 0.467 21 > 1.9 x 1025 < 350
76Ge 0.117 3.5 > 1.6 x 1025 < 330 - 1350
76Ge 0.943 61 = 1.2 x 1025 = 440
82Se 7 x 10-5 0 > 2.7 x 1022
(68%)< 5000
100Mo 5 x 10-4 4 > 5.5 x 1022 < 2100
116Cd 1 x 10-3 14 > 1.7 x 1023 < 1700
128Te Geochemical NA > 7.7 x 1024 < 1100-1500
130Te 0.025 5 > 5.5 x 1023 < 370 - 1900
136Xe 7 x 10-3 16 > 4.4 x 1023 < 1800-5200
150Nd 6 x 10-5 0 > 1.2 x 1021 < 3000
Recent claim of 0ββ detection
Heidelberg-Moscow
71.7 Kg-y data
Controversial Results
Increased interest in
quasi-degenerate 76Ge
experiments
0ββ ProposalsCollaboration 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) < 1 Xe TPCGEM 76Ge (11) ≈ 0.8 Ge detectors in LNGENIUS 76Ge (8.8) ≈ 0.6 Ge detectors in LNGSO 160Gd (1.7) Gd2SiO5 crystals in
liquid scintillatorMajorana 76Ge (3.5) ≈ 1 Segmented Ge detectorsMOON 100Mo (2.5) ≈ 8 Mo foils and plastic
scintillatorMPI bare Ge 76Ge (8.8) Ge detectors in LN
Nano-crystals ≈ 100 kmol Suspended nanoparticles
Super-NEMO 82Se (0.6) ≈ 1 Foils with trackingXe 136Xe (6.3) ≈ 118 Xe dissolved in liquid
scintillator XMASS 136Xe (6.1) Liquid Xe
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
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
Majorana
MOON (Mo Observatory of Neutrinos)
Uses unique nuclear
structure of 100Mo to
combine 0ββ search
and solar neutrino
experiment
Modules of plastic fiber
scintillators with thin
layers Mo
MOON
Acknowledgements
I would like to thank Richard Ferrieri and
all of the TA’s, professors, students and
supporters of the BNL Nuclear and
Radiochemistry Summer School