1. Double Beta Decay review
Fabrice Piquemal
CENBG, University Bordeaux 1 CNRS/IN2P3
and Laboratoire Souterrain de Modane (CNRS/IN2P3-CEA/DSM)
Thanks to: G. Gratta, S. Elliot, A. Giuliani, S. Schoenert,
T. Kishimito, M. Nomachi, K. Zuber, M. Chen
F. Piquemal (CENBG) LP07

2. Double Beta decay: physics case
- Leptonic number violation
- Nature of neutrino : Dirac (n n) or Majorana (n =n)
- Absolute neutrino mass and neutrino mass hierarchy
Right-handed current interaction
CP violation in leptonic sector
Search of Supersymmetry and new particles

3. Accelerators (K2K,Minos)
Neutrino properties
Oscillations
Atmospheric (SK)
Accelerators (K2K,Minos)
Reactors (CHOOZ)
Accelerators (JPARC)
Solar (SNO, SK)
Reactors (KamLAND) U
,b : CP Majorana phase
tan223=1.0 ± sin2213 < tan212=0.39 ± 0.05
CP= CP Dirac phase
m2atm = m231 = (2.3  0.2 ) 10-3 eV2
m2sol = m212 = (7.9  0.3) 10-5 eV2

4. Neutrino mass Absolute mass ? Beta decay mv = S |Uei| mi <2.3 eV
1/2 2 2
Beta decay mv = S |Uei| mi <2.3 eV
Double beta decay |<mn>| = |SUei mi| < eV
Cosmology mi = m1+m2+m3 <~1 eV 2 m2
m12
m22
m32
Degenerate
m1≈m2≈m3» |mi-mj|
Normal hierarchy
m3>>> m2~m1
Inverted hierarchy
m2~m1>>m3 ?
Mass hierarchy ?

5. Double Beta decays bb(2n) bb(0n) e- e- e- e- n n DL =2 bb
Single beta decay forbidden (energy)
or strongly suppressed by large angular
momentum change
Decay to ground state or excited states bb bb
bb(2n)
bb(0n) e- e- e- e- n n
DL =2
2nd order process of weak interaction
Already observed for several nuclei
bb(0n)  Majorana neutrino (n=n)

6. Neutrinoless Double Beta decay
(A,Z) (A,Z+2) + 2 e-
Discovery implies DL=2 and Majorana neutrino
Process: parameters
Light neutrino exchange
<mn>
(V+A) current
<mn>,<l>,<h>
Majoron emission
<gM>
SUSY
l’111,l’113l’131,…..
R-parity violation T1/2 depends on
(l’111)2, gluino and squarks mass
T1/2= F(Qbb,Z) |M|2 <mn>2 -1
Phase space factor
Nuclear matrix element
Effective mass:
<mn>= m1|Ue1|2 + m2|Ue2|2.eia1 + m3|Ue3|2.eia2
|Uei|: mixing matrix element
a1 et a2: Majorana phase 5
T1/2= F |MJ|2 <gM>2 -1
Phase space factor
Nuclear matrix element
Coupling between Majoron and neutrinos

7. bb(0n) observables
From G. Gratta

8. bb(0n) observables Light neutrino exchange V+A current
Minimum electron
energy
MeV
MeV
Angular distribution
betwen the 2 electrons
Cosq
Cosq

9. Effective neutrino mass and neutrino oscillations
Inverted hierarchy
Normal hierarchy
Degenerated
Degenerate: can be tested
Inverted hierarchy: tested by the next
generation of bb experiment
<mn> in eV
Normal hierarchy: inaccessible

10. Isotopic abundance (%)
bb emitters
Isotope
Q (MeV)
Isotopic abundance (%)
G0(yr-1) x 1025
48Ca
4.271
0.187
2.44
76Ge
2.040
7.8
0.24
82Se
2.995
9.2
1.08
96Zr
3.350
2.8
2.24
100Mo
3.034
9.6
1.75
116Cd
2.802
7.5
1.89
130Te
2.528
33.8
1.70
136Xe
2.479
8.9
1.81
150Nd
3.367
5.6
8.00

11. Nuclear matrix elements5
T1/2= F(Qbb,Z) |M0n|2 <mn>2 -1
Nuclear matrix elements are calculated using various models:
QRPA (RQRPA, SQRPA, …….)
Shell model
Up to recently no convergence for the results
Statement from Bahcall et al. to use the nuclear matrix range as an uncerntainty:
« Democratic approach »
Does not take into account the improvements of the Models
Exchanges between groups to understand discrepencies and to evaluate errors
bb(2n) is used by QRPA to fix gpp paramaters for QRPA

12. Nuclear matrix elements
Shell Model (Poves et al) - QRPA
Two different QRPA calculations
A lot of improvements have been done but still discrepancies
Uncertainties for extraction of <mn>
In the following, « latest NME » will refer to these Nuclear Matrix Elements

13. View of the field: present and future
Today experiments have a mass of enriched source ~10 kg
To reject inverted hierarchy mass scenario, enriched source mass  1 ton
All projects have this goal but it is unrealistic to plane to go directly
from 10 kg to 1 ton scale (understanding and control of the background)
Intermediate step at 100 kg scale is needed (as proposed by each project)
Talk focuses on the running experiments, on some 100 kg scale
projects starting within 5 years and R&D projects.

14. (Loaded) Scintillator
Experimental techniques
With background:
M: masse (g)
e : efficiency
KC.L.: Confidence level
N: Avogadro number
t: time (y)
NBckg: Background events (keV-1.g-1.y-1)
DE: energy resolution (keV)
> e A
M . t
NBckg . DE
ln2 . N
kC.L.
(y)
Today, no technique able to optimize all the parameters
Calorimeter
Semi-conductors
Source = detector
Calorimeter
(Loaded) Scintillator
Source = detector
Tracko-calo
Source  detector
Xe TPC
Source = detector b b b b b b b b
e, DE
e, M
NBckg, isotope choice
e,M, (NBckg)
F. Piquemal (CENBG) LP07

15. Calorimeter vs Tracko-calo
High energy resolution
Modest background rejection
High background rejection
Modest energy resolution
bb(0n)
bb(0n)
keV
bb(0n)
bb(0n)
keV
MeV

16. Qbb and background components
Natural radioactivity (40K, 60Co,234mPa, external 214Bi and 208Tl…)
214Bi and Radon
208Tl (2.6 MeV g line) and Thoron
g from (n,g) reaction and muons bremstrahlung
+ more specific background for calorimeter
Surface or bulk contamination in a emitters
cosmogenic production
150Nd
96Zr
100Mo
82Se
130Te
76Ge
48Ca
76Xe 3 4 5 2
Qbb MeV
+ bb(2n) for tracko-calo or calorimeter with modest energy resolution

17. bb(0n) search is a very dynamic field
Experiments
Isotopes
Techniques
Main caracteristics
NEMO3
100Mo,82Se
Tracking + calorimeter
Bckg rejection, isotope choice
SuperNEMO
82Se, 150Nd
Cuoricino
130Te
Bolometers
Energy resolution, efficiency
CUORE
GERDA
76Ge
Ge diodes
Energy resolution, eficiency
Majorana
COBRA
130Te, 116Cd
ZnCdTe semi-conductors
EXO
136Xe
TPC ionisation + scintillation
Mass, efficiency, final state signature
MOON
100Mo
Compactness, Bckg rejection
CANDLES
48Ca
CaF2 scintillating crystals
Efficiency, Background
SNO++
150Nd
Nd loaded liquid scintillator
Mass, efficiency
XMASS
Liquid Xe
CARVEL
CaWO4 scintillating crystals
Yangyang
124Sn
Sn loaded liquid scintillator
DCBA
Gazeous TPC
Bckg rejection, efficiency

18. bb(0n): Present situation
Ge diode detectors:
High energy resolution and efficiency
But poor background rejection (pulse shape analysis)
Heidelberg-Moscow (2001)
~11 kg of enriched 76Ge (86%)
IGEX (2002)
~ 8.4 kg of enriched 76Ge (86%)
35.5 k.yr
8.9 kg.yr without PSA
4.6 kg.y with PSA
0.06 cts/keV/kg/yr
T 1/2 > yr (90% CL)
T 1/2 > yr (90% CL)
<mn> < eV (90% CL)
<mn> < eV (90% CL)
Eur. Phys. J., A 12 (2001) 147
Phys. Rev. D65 (2002)

19. bb(0n) signal ? HM claim 2006: Improvement of PSA (6s) 2004 (4s)
+0.44
T1/2 = yr
T1/2 = (0.69 – 4.18) 1025
<mn> = (90%)
-0.31
<mn> = 0.32 ± eV

20. Ge detector improvements
Strategies: Ge detectors in liquid nitrogen to remove materials
Active shielding and segmentation of detectors to
reject gamma-rays e- 
detector
segments
Liquid argon
scintillation
crystal anti-coincidence
Detector segmentation
pulse shape analysis
R&D: liquid argon anti-coincidence

21. GERDA (Germany, Italy, Belgium, Russia) Removal of matter
Use of liquid nitrogen or argon for active shielding
Segmentation
Improvement of Pulse Shape Analysis
PHASE I: 17.9 kg of enriched 76Ge (from HM and IGEX)
In 1 year of data if B=10-2 cts/keV/kg/yr (check of Klapdor’s claim)
Start 2009 at Gran Sasso, results T1/2 > yr <mn> < 250 meV
PHASE II: 40 kg of enriched 76Ge (20 kg segmented)
if B=10-3 cts/keV/kg/an T1/2 > yr in 3 years of data <mn> < 110 meV
PHASE III: if PHASE I and II succeed 1 ton if B=10-3 cts/keV/kg/yr
T1/2 > yr in 3 years of data <mn> < 20 meV

22. Majorana Goal 500 kg of 76Ge (modules of 60 kg) Very pure material
(USA, Russia, Japan)
Very pure material
(Electroformed cooper)
Segmentation
PSD improvement
Deep underground
Goal 500 kg of 76Ge (modules of 60 kg)
R&D phase kg of 86% enriched 76Ge crystals
Some of the crystals segmented
Bckg goal ~ 1 count/ROI/t-yr (after analysis cuts)
30 kg of enriched Ge, running 3 yr. Data taking scheduled for 2011
T1/2 > yr <mn> < 140 meV (could confirme or refute Klapdor’s claim)
Collaboration with Gerda for 1 ton detector

23. Cuoricino Bolometers of TeO2 (Qbb= 2.528 MeV) Heat sink
Bolomètres: CUORICINO
Bolometers of TeO2 (Qbb= MeV)
Heat sink
Signal:∆T = E/C
Thermometer
Double beta decay
Crystal absorber
High energy resolution 5-7 keV (FWHM)
Natural abundance for 130Te: 34%
High efficiency: 86%
But no electron identification
Background from internal and surface
contamination in a emitters
214Bi
(238U chain)
208Tl
(232Th chain)
60Co
pile up
5.3 kg.an
T1/2 > ans (90%)
<mn> <0.5 – 2.4 eV
bb(0n)
Energy (keV)
10.4 kg of 130Te
Running at Gran Sasso since 2003
F. Piquemal (CENBG) LP07

24. Cuoricino results 0DBD 11.83 kg.yr
Gamma region, dominated by gamma and beta events,
0DBD
Alpha region, dominated by alpha peaks
(internal or surface contaminations)
Bckg: 0.18 cts/keV/kg/yr
60Co
pile up
130Te
0vBB
11.83 kg.yr
Energy (keV)
T1/2 > yr (90% CL) <mn> < 0.2 – 1 eV (90% CL)
Expected final sensitivity ~2009: T1/2 > yr <mn> < 0.1 – 0.7 eV

25. Array of 988 TeO2 5x5x5 cm3 crystals
CUORE
(Italy, USA,Spain)
750 kg of TeO2  kg of 130Te
Array of 988 TeO2 5x5x5 cm3 crystals
Improvement of surface event rejection
Goal :Nbckg=0.01 cts.keV-1.kg-1.yr-1
(Factor 20 compared to Cuoricino)
Data taking foreseen in 2011
(R&D on other bolometers like 116CdWO4)
Expected sensitivities (5 years of data)
Nbckg=0.01 cts.keV-1.kg-1.yr-1
T½ > yr
<mn> < 0.03 – 0.17 eV
Nbckg=0.001 cts.keV-1.kg-1.yr-1
T½ > yr
<mn> < – 0.1 eV
F. Piquemal (CENBG) LP07

26. NEMO 3 Tracko-calo detector e- e- bb events
(France, UK, Russia, Spain, USA, Japan, Czech Republic,Ukraine, Finland)
Tracko-calo detector
Central source foil (~50 mm thickness)
Tracking detector (6180 drift cells)
t = 0,5 cm, z = 1 cm ( vertex )
Calorimeter (1940 plastic scintillators + PMTs)
Efficiency 8 %
Running at Modane Underground lab since 2003 E1 e-
Vertex
Multi-isotopes (7 kg of 100Mo, 1 kg of 82Se,…)
Identification of electrons
Very good bckg rejection (< 10-3 cts/keV/kg/yr)
Angular distribution and single electron energy
(necessary to distinguish the mechanism in case
of discovery)
But modest energy resolution and efficiency e-
E1+E2= 2088 keV
t= 0.22 ns
(vertex) = 2.1 mm E2
bb events
F. Piquemal (CENBG) LP07

27. NEMO3: bb(0n) results 100Mo
Phase I, High radon
7.6 kg.yr
Phase II, Low radon
5.7 kg.yr
Phase I + II
13.3 kg.yr
Number of events / 40 keV
Number of events / 40 keV
Number of events / 40 keV
[ ] MeV: e(bb0n) = 8 %
Expected bkg = 8.1 events
Nobserved = 7 events
[ ] MeV: e(bb0n) = 8 %
Expected bkg = 3.0 events
Nobserved = 4 events
[ ] MeV: e(bb0n) = 8 %
Expected bkg = 11.1 events
Nobserved = 11 events
Phases I + II
T1/2(bb0n) > yr (90 % C.L.) <mn> < 0.6 – 1.3 eV
T1/2(bb0n) > yr (90 % CL) <mn> < 0.3 –0.7 eV
Expected in 2009

28. SuperNEMO project Tracko-calo with 100 kg of 82Se or 150Nd
(France, UK, Russia, Spain, USA, Japan, Czech Republic,Ukraine, Finland)
Tracko-calo with 100 kg of 82Se or 150Nd
(possibility to produce 150Nd with the French AVLIS facility)
T½ > yr <mn> < 0.05 – 0.09 eV
Modules based on the NEMO3 principle
Measurements of energy sum, angular distribution
and individual electron energy
3 years R&D program: improvement of energy resolution
Increase of efficiency
Background reduction
…….
100 kg 20 modules
R&D funded by France, UK and Spain
2009: TDR
2011: commissioning and data taking of first modules in Canfranc (Spain)
2013: Full detector running

29. EXO Liquid Xe TPC Energy measurement by ionization + scintillation
(USA, Canada, Switzerland, Russia)
Liquid Xe TPC
Energy measurement by ionization + scintillation
Tagging of Baryum ion (136Xe  136Ba e-)
Large mass of Xe
Identification of final state  background rejection
But no e- identification
Poor background rejection without Ba ion tagging
R&D for Ba ion tagging in progress
Prototype EXO-200
200 kg of 136Xe, no Ba ion tagging
Installation in progress in WIPP underground lab 2007
Could measure bb(2n) of 136Xe
EXO 200 (2 years) T½ > yr (90% CL) <mn> < eV

30. CANDLES (Japan) Pure CaF2 crystals Wave length shifter in LS
PSD to reject g and a
CaF2(Pure)
Liquid Scintillator
(Veto Counter)
Buffer Oil
Large PMT
Efficiency, 48Ca (background)
But mass of isotope, no e- identification
CANDLES III : Prototype 103 cm3 × 60 crystals kg (~ 350g of 48Ca)
In test in Osaka University
Full detector 103 cm3 × 96 crystals kg
Installation in spring 2008 at Kamioka
Expected BG: 0.14 event/yr (30 mBq/kg)
<mn> ~0.5 eV
CANDLES IV : 3 tons of CaF2 (3 mBq/kg) 6 yr <mn> ~0.1 eV

31. MOON Compact tracko-calo Compactness Multi-isotopes
(Japan, USA)
Compact tracko-calo
Compactness
Multi-isotopes
Electron identification
But energy resolution and
bckg rejection (ToF)
Moon 1: Data acquisition with 142 g of 100Mo (40 mg/cm2)
In progress: Improvement energy resolution
Waveform readout
Design of a module
Module: kg of bb source <m> ~100 meV

32. DCBA (Japan) Drift Chamber beta-ray Analyser Electron identification
Multi-isotopes
But Efficiency, Energy resolution
Prototype with 207Bi :
10% (FWHM) energy resolution
X position s= 0.5 mm
Y position s= 0.02 mm
X position s= 6 mm

33. COBRA Good energy resolution Several isotopes at the same time
(UK, Germany, Italy, poland, Slovaquia, Finland, USA)
Array of 1cm3 CdZnTe detectors
Good energy resolution
Several isotopes at the same time
Efficiency
But background rejection
4x4x4 detector array = 0.42 kg CdZnTe
Installed at LNGS
Test of coincidence rejection
Measure of 113Cd
Cd-113 beta decay with half-life of about 1016 yrs
F. Piquemal (CENBG) LP07

34. SNO++ Scintillator loaded with Nd. Mass Efficiency
But energy resolution
No e- identification
Test of light attenuation
Study of Nd purification (factor 1000
per pass in Th and Ra)
56 kg of 150Nd (0,1 % of natural Nd)
4 yr of data <mn> ~80 meV
500 kg of 150Nd 4yr <mn> ~30 meV
500 kg of 150Nd
1 year
<mn> = 150 meV
only internal Th and 8B solar neutrino backgrounds are important
Similar prospect in KamLAND
F. Piquemal (CENBG) LP07

35. Enriched isotope mass (kg)
Summary
Summary
Experiment
Isotope
Enriched isotope mass (kg)
T1/2 (yr)
<mn> (eV)
Start
Status
CUORE
130Te
203 *
2011
Funded
GERDA phase I
phase II
76Ge
17.9 40
0.2 – 0.5*
0.07 – 0.2*
2009
Majorana
1.1026
0.1 – 0.3*
EXO-200
136Xe
200 *
2008
SuperNEMO
82Se
150Nd
100
1026 *
0.07
R&D
CANDLES
48Ca
0.5
~0.5
MOON II
100Mo
120
0.09 – 0.13 ?
DCBA 20
SNO++
500
0.03
COBRA
116Cd,
420
* Calculation with NME from Rodim et al., Suhonen et al., Caurier et al. PMN07

36. <mn> current and future limits. HM
Cuoricino
NEMO3
Klapdor
claim
Limits in 2009
HM,NEMO3,
Inverted hierarchy
Normal hierarchy
Degenerated
Expected limits
2009 – 2015
CUORE,GERDA,
Majorana,
SuperNEMO,
EXO,….
Use of « latest NME » for all experiments

37. Summary Summary Very active field. A claim to be checked
Current experiments will reach a sensitivity on <mn> ~(0.2 – 0.7) eV in 2009
Need to measure several nucleus with different techniques (only tracko-calo
could distinguish the mechanism in case of discovery)
Next generation ~ source mass 100 – 200 kg <mn> ~ (0.03 – 0.1) eV
Will cover partially the inverted hierarchy mass scenario (2011 – 2015)
Essential step for 1 ton scale experiment ( background considerations)
Need improvements for Nuclear Matrix Element calculations

38. bb(0n): Present situation
Pulse shape analysis with Ge detectors
SSE
(Multiple Site Event)
(Single Site Event)
SSE
MSE
F. Piquemal (CENBG) LP07