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