Search for neutrinoless double
beta decay with NEMO 3 and
SuperNEMO experiments
Vladimir Vasiliev
UCL, London, UK
on behalf of the NEMO collaboration
SUSY 2007
Karlsruhe, 28 July 2007
bb decay, n mass mechanism
predicted in 1935 by
Maria Goeppert-Mayer
DL = 2 - only possible for
Majorana neutrinos with mass > 0
Beyond the SM:
Lepton Number Violation !
1-5 July 2007, ILIAS meeting, Blaubeuren
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bb decay and SUSY: R-parity breaking
L  'ijk LQD
dR+dR → uL+uL+eL+eL
exchange with:
squarks
neutralinos
gluinos
related to ('111)2
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bb decay and SUSY: squark mixing
L  'ijk LQD
dR+dR → uL+uL+eL+eL
Mixing between Land R- handed
fermion
superpartners.
Paes, Hirsch,Klapdor-Kleingrothaus, PLB 459(1999) 450
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bb decay and SUSY: neutrino mass
L  'ijk LQD
dR+dR → uL+uL+eL+eL
neutrino acquires
mass due to SUSY
radiactive corrections
Gozdz, Kaminski, Šimkovic, PRD 70 (2004) 095005
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bb decay mechanism
If observed, how to determine mechanism: n mass,
SUSY, V+A ... ???
• measure kinematical parameters: angular correlation,
individual electron energy!
• measure several isotopes!
• measure bb0n decay to excited state of final nuclei!
Calorimetry plus tracking approach:
Detection of both electrons, three kinematic observables: individual electron
energies; angular correlation; energy sum
Sources separated from the detector: measure T½ for several isotopes
Particle identification: e-, g; good signature for decay to excited states
Unique and complementary
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key techniques: tracking, calorimetry, timing
NEMO-3
 Goal: reconstruct 2 electrons of the final
state
20 sectors
 E1 + E2 = Qbb
 Particle physics - like approach:
 Measure several observables of the final
state
Trajectories of 2 electrons
Energies of 2 electrons
Time
Magnetic field curvature ("+" vs "-")
 Reconstruct the final state topology and
kinematics
 Several requirements for candidate
events
3m




 Topology (vertex, track-scintillator
correlation)
 Time coincidence
 2-electron invariant mass
 Identify e-, e+, g, a
 Able to measure backgrounds
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B (25 G)
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Multi source detector
bb2n measurement
116Cd
405 g
Qbb = 2805 keV
96Zr
9.4 g
Qbb = 3350 keV
150Nd
37.0 g
Qbb = 3367 keV
48Ca
7.0 g
Qbb = 4272 keV
130Te
454 g
Qbb = 2529 keV
100Mo
6.914 kg
Qbb = 3034 keV
82Se
0.932 kg
Qbb = 2995 keV
natTe
893 g
Cu
621 g
Detector bkg
measurement
bb0n search
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Sector interior view
cathode rings
wire chamber
PMTs
Calibration tube
scintillators
bb isotope foils
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Installation in Modane
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Installation in Modane
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With shielding
water tank
wood
coil
iron shield
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Full detector now
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Typical bb2n event observed from 100Mo
Transverse view
Run Number: 2040
Event Number:
9732
Date: 2003-03-20
Longitudinal
view
Vertex
emission
Vertex
emission
Deposited energy:
E1+E2= 2088 keV
Internal hypothesis:
(Dt)mes –(Dt)theo = 0.22 ns
Common vertex:
(Dvertex) = 2.1 mm
(Dvertex)// = 5.7 mm
Criteria to select bb events:
• 2 tracks with charge < 0
• 2 PMT, each > 200 keV
• PMT-Track association
• Common vertex
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100Mo
6.914 kg
Qbb = 3034 keV
• Internal hypothesis TOF (external event rejection)
• No other isolated PMT (g rejection)
• No delayed a track (214Bi rejection)
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NEMO backgrounds
•Natural
radioactivity:
• U/Th chain
• 40K
• Rn
•cosmic m
•neutrons
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External
double
Compton
Compton +
Moller
b- +Compton
b- +Moller
pair
production
Internal
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b- +IC
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Backgrounds: Radon purification facility
Running since Oct. 4th, 2004 in FréjusUnderground Lab.
1 ton charcoal @ -50oC, 7 bars
Flux: 150 m3/h
Activity of 222Rn :
Before Facility = 15 Bq/m3
After Facility < 15 mBq/m3
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Radon purification facility, effect inside NEMO3
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Backgrounds: bb-like events from Cu
- background sources simulated using Monte Carlo
- radioactivity rates from material tests in HPGe and control channel meas's
Phase II data; ~ 1.5 y.
MC prediction: 130 ev.
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Sum energy spectrum
12000
10000
219 000 events
6914 g
389 days
S/B = 40
NEMO-3
100Mo
8000
• Data
2b2n
Monte Carlo
Background
subtracted
6000
4000
Number of events
Number of events/0.05 MeV
NEMO 3 highlights: 2b2n 100Mo
Angular distribution
12000
10000
219 000 events
6914 g
389 days
S/B = 40
NEMO-3
100Mo
8000
6000
• Data
2b2n
Monte Carlo
Background
subtracted
4000
2000
2000
0
0
E1 + E2 (MeV)
Cos()
T1/2(bb2n) = 7.11  0.02 (stat)  0.54 (syst)  1018 years
Phys. Rev. Lett. 95 182302 (2005)
«bb factory» → tool for precision test
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NEMO 3 highlights: 2b2n preliminary
82Se
932 g
389 days
2750 events
S/B = 4
Preliminary results for ~360 d Phase I data. Additional
statistics is being analysed and to be published soon.
82Se
T1/2 = 9.6 ± 0.3 (stat) ± 1.0 (syst)  1019 y
116Cd
T1/2 = 2.8 ± 0.1 (stat) ± 0.3 (syst)  1019 y
150Nd
T1/2 = 9.7 ± 0.7 (stat) ± 1.0 (syst)  1018 y
96Zr
T1/2 = 2.0 ± 0.3 (stat) ± 0.2 (syst)  1019 y
48Ca
T1/2 = 3.9 ± 0.7 (stat) ± 0.6 (syst)  1019 y
48Ca
Background subtracted
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NEW in 2007: direct meas. of 130Te 2b2n
The bb2n half-life of 130Te has been a long-standing mystery::
Geochemical:
- (25 ± 2) x 1020 years (Kirsten 83)
- (27 ± 2) x 1020 years (Bernatowicz 93)
- (7.9 ± 1) x 1020 years (Takaoka 96)
- ~8 x 1020 years (Manuel 91)
Difference between ‘old’ and ‘young’ ores due to
time dependence of constants..?
Ratio of 82Se/130Te (less systematics):
-(9 ± 1) x 1020 years (average by A. Barabash)
Direct measurement:
-(6.1 ± 1.4 (syst) ± 2.9 3.4) x 1020 years (Arnaboldi 2003)
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NEW in 2007: direct meas. of 130Te 2b2n
109 events
607 events
534 days, 454 g of 130Te
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background subtracted
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NEMO 3 highlights: 2b0n 100Mo & 82Se
100Mo,
Phase I + II, 693 days
82Se
,Phase I + II, 693 days
T1/2bb0n > 2.1 x 1023 (90 % CL)
T1/2bb0n > 5.8 x 1023 (90 % CL)
<mn>* < 1.4-2.2 eV
<mn>* < 0.8 – 1.3 eV
'111 < 2.5 10-4
'111 < 1.5 10-4
T1/2bb0n > 8 x 1023 (90 % CL)
expected in 2009: T1/2bb0n > 2 x 1024 (90 % CL)
<mn>* < 0.7-1.1 eV
<mn>* < 0.4 – 0.7 eV
Collaboration decided to perform blind analysis with mock data
Plan to open the box and update the results ~ summer 2008 and again ~ early 2010.
* Recent QRPA NME calculation as in MEDEX'07
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'Majoron' search
Axions  (‘Majorons’) with coupling
to neutrinos
best limits
n=1 **
n=2 **
n=3 **
n=7 **
Mo
>2.7∙1022
gee<(0.4-1.8)∙10-4
>1.7∙1022
>1.0∙1022
>7∙1019
Se
>1.5∙1022
gee<(0.7-1.9)∙10-4
>6.0∙1021
>3.1∙1021
>5.0∙102
0
n: spectral index, limits on half-life in years
** PI
1-5 July 2007, ILIAS meeting, Blaubeuren
data, R.Arnold et al. Nucl. Phys. A765 (2006) 483
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SuperNEMO project
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~ 60 physicists, 27 laboratories, 12 countries,
USA
MHC
INL
(U Texas)
UK
UC London
U Manchester
Imperial College
Spain
U Valencia
U Zaragoza
U Barcelona
Japan
U Saga
KEK
U Osaka
Marocco
Fes U
Finland
U Jyvaskula
Poland
U Warsaw
Ukraine
INR Kiev
ISMA Kharkov
France
CEN Bordeaux
IReS Strasbourg
LAL Orsay
LPC Caen
LSCE Gif/Yvette
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Russia
JINR Dubna
ITEP Mosow
Kurchatov Institute
Slovakia
(U. Bratislava)
Czech Republic
Charles U Praha
IEAP Praha
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Very preliminary SuperNEMO design
Planar and modular design: ~ 100 kg of isotope (~20 modules  5-7 kg)
1 module:
Source (~40 mg/cm2) 4 (length) x 3(height) m2
Tracking : drift chamber ~3000 cells in Geiger
mode
Calorimeter: scintillators + PM
~1 000 PM if scint. blocks
~ 100 PM if scint. bars
Top view
1m
5m
5m
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Very preliminary SuperNEMO design
Single sub-module
with ~7 kg of isotope
5m
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~20 sub-modules for 100+ kg of isotope
surrounded by shielding
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SuperNEMO design study
February 2006 – January 2009
• Approved in UK, France and Spain. Similar
proposals under consideration in Russia, Czech
Republic, Japan
• Main tasks and deliverables
– R&D on critical components
•
•
•
•
•
Calorimeter energy resolution of 4% at 3 MeV
Optimisation of tracking detector and construction (robot)
Better background rejection (e.g. extra veto counters)
Ultrapure source production and purity control
Simulations and geometry optimisation
– Technical Design report
– Experimental site selection (Frejus, Canfranc, Gran
Sasso, Boulby)
5m
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R&D: SuperNEMO calorimeter
•
•
•
Goal: FWHM  7%/E  4% at 3 MeV (Currently 14-16%/E in NEMO3)
A combination of energy losses in the foil and calorimeter DE/E
Studies
– Organic (plastic or liquid),
– Shape, size, coating
– PMTs (Photonis, Hamamatsu, ETL)
– Light guides, optical contact
– Chemistry
High QE Hamamatsu
tube
=
+
See Jean-Stephane's talk for details
1-5 July 2007, ILIAS meeting, Blaubeuren
BC404
scintillator
wraped in
teflon
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DE/E = 6.5%
at 1 MeV

3.8% at 3 MeV
if 1/E
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R&D: tracker optimisation
 optimize:
 wire length and diameter
 wire material and diameter,
 read-out, gas mixture etc
 9-cell prototype built
 90 cell prototype + 300 cell prototype to be
built by Spring 2008
 About 500k wires to be strung, crimped,
terminated => wire robot under development
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R&D : radio purity and BiPo device
 Need to measure radio purity at a few mBq/kg level
 Beyond sensitivity of conventional Ge detectors
 Build new tool, BiPo detector.
Bi-Po Process
238U
b
214Po
a
214Bi
(19.9 mn)
210Pb
0.021%
e- prompt
(164 ms)
22.3 y
Scintillator + PMT
e-
e-
Tracking
(wire chamber)
a delay
210Tl
(1.3 mn)
a
232Th
b
212Po
(300 ns)
Shield
radon, neutron,g
a
212Bi
(60.5 mn)
36%
Delay a
Source foil
(40 mg/cm2)
208Pb
(stable)
208Tl
(3.1 mn)
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R&D: isotope enrichment/ purification
• 4 kg of 82Se funded by ILIAS
have been delivered from Russia.
• purification at ILN (US) underway
• enrichment of Nd possible in France
(MENPHIS, currently mothballed)
Choice of nucleus depends on:
enrichment possibilities
• high Q
bb value
 larger phase space
 lower non-bb background
• small bb2n contribution
•
Two main options:
G0n(150Nd) / G0n(82Se) = 8
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Qbb
(MeV)
Isotopic
Abundance
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SuperNEMO schedule summary
2007
2008
2010
2009
2011
2012
2013
NEMO3 Running
R&D SuperNEMO
BiPo1
Canfranc
TDR
BiPo construction
BiPo
installation
BiPo running @ Canfranc
SuperNEMO 1st
module construction
Preparation
of the site
construction of
20 modules
6 SuperNEMO modules running @
Canfranc
Final SuperNEMO modules installation
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RUNNING of
Full detector
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Conclusion
NEMO’s Tracking+Calorimetry approach is unique:
-high background rejection
- choice of isotopes
- reconstruction of kinematics
NEMO 3 is taking data:
-bb2n factory, important for understanding of backgrounds and NME
-limits on bb0n using different isotopes:
-T1/2 (0n > 5.8 x 1023 y @ 90% CL for 100Mo  <mn> < 0.8-1.3 eV (693
days); '111 < 1.5 x 10-4
-limits on Majoron's coupling
-T 1/2(2n) = (7.6 ± 1.5 (stat) ± 0.8(syst)) x 1020 y for 130Te
SuperNEMO R&D approved in France, the UK and Spain; TDR
expected in 2008; full 20 modules in 2012-2013
-choice of isotopes: 82Se or 150Nd
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Backup slides
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