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Search for neutrinoless double b decay
in
NEMO-3 and SuperNEMO experiments
Zenon Janas
for
Warsaw - NEMO initiative group
Warszawa, 03.07.2006
Warsaw - NEMO initiative group
W. Dominik, IFD UW
Z. Janas, IFD UW
T. Matulewicz, IFD UW
M. Pfutzner, IFD UW
E. Rondio, SINS
........
Double beta decay
(A, Z+1)
(A, Z)
bb
(A, Z+2)
Main bb decay modes:
 2nbb
(A, Z)  (A, Z+2) + 2 e + 2 ne
DL = 0
 0nbb
(A, Z)  (A, Z+2) + 2e
DL = 2
arbitrary units
Energy spectra of emitted electrons
(Qbb ~ MeV)
Neutrinoless bb decay rate
T 
0 n 1
1/ 2
G
0v
 M
0n
2
 m bb
2
Motivation of 0nbb decay studies
• neutrino nature: Dirac or Majorana ?
• absolute neutrino mass scale
• neutrino mass hierarchy
• Majoron emission ?
Experimental approaches in bb decay studies
Calorimeter
Tracking + calorimeter
HPGe – Te bolometers
NEMO
only total energy measured
individual electrons observed
high energy resolution
modest energy resolution
good efficiency
small efficiency
compact detectors ( 10 m)
large detector size ( 50 m)
very pure crystals
background measured
source specific
universal
Both techniques are complementary !!
NEMO-3 detector
Location: Fréjus Underground Lab.
20 sectors
4800 m.w.e.
Source: 10 kg of bb isotopes (100Mo)
cylindrical, S = 20 m2, 60 mg/cm2
Tracking detector:
drift wire chamber operating
in Geiger mode (6180 cells)
3m
Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O
Calorimeter:
1940 plastic scintillators
coupled to low radioactivity PMTs
B (25 G)
Ability to identify e, e+, g and a
© S. Julian, LAL
Typical 2nbb event observed from 100Mo isotope
Transverse view
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
Criteria to select bb events
• 2 tracks with charge < 0
• 2 PMT, each > 200 keV
• PMT-Track association
• Common vertex
• Internal hypothesis
(external event rejection)
• No other isolated PMT (g rejection)
• No delayed track (214Bi rejection)
(Dvertex)// = 5.7 mm
Trigger: at least 1 PMT > 150 keV
 3 Geiger hits (2 neighbour layers + 1)
Trigger rate = 5.8 Hz
bb events: 1 event every 2.5 minutes
2nbb decay of 100Mo
Sum Energy Spectrum
Angular Distribution
219 000 evnts
6914 g
389 days
Data
2nbb sim.
bgnd
E1 + E2 (MeV)
219 000 evnts
6914 g
389 days
Data
2nbb sim.
bgnd
cos(ee)
T1/2(100Mo,2nbb) = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ]  1018 y
0nbb decay of 100Mo
2.8 - 3.2 MeV range
Nobserved = 7 events
bgnd
= 8.1 ± 1.3
T1/2(100Mo,0nbb) > 4.6  1023 y
<mn> < 0.7 – 2.8 eV
R. Arnold et al., PRL 95 (2005) 182302
SuperNEMO - preliminary design
Plane geometry, 20 modules
1 module:
source: 34 m2  40 mg/m2 of enriched isotope
tracking volume: ~ 3000 drift chamber cells
calorimeter: ~ 1000 scintillators + PMTs
1m
5m
Top view
© S. Julian, NEMO-3 collaboration
From NEMO-3 to SuperNEMO
NEMO-3
SuperNEMO
100Mo
82Se
T1/2(bb2n) = 7 x 1018 y
7 kg
Isotope
Mass of isotope
e (bb0n) = 8 %
Efficiency
~ 11 % at 3 MeV
Resolution
~ 1 evt / 7 kg / y
T1/2(bb0n) > 2 x 1024 y
<mn> < 0.3 – 1.3 eV
208Tl
and 214Bi
background
SENSITIVITY
after 5 years
T1/2(bb2n) = 1020 y
100 kg
e (bb0n) ~ 20 %
~ 7 % at 3 MeV
~ 1 evt/ 100 kg / y
T1/2(bb0n) > 2 x 1026 y
<mn> < 0.04 – 0.1 eV
Most promissing 0nbb projects
A.S. Barabash, arXiv:hep-ex/0602037
Plans for SuperNEMO
2005 - 2007 - R&D program
2008
- construction of the SuperNEMO module with 5 kg 82Se
2009 - 2011 - construction and installation of the 20 modules,
start taking data with delivered modules
2012
- full SuperNEMO running with 100 kg of 82Se
R&D tasks in the SuperNEMO collaboration
SuperNEMO collaboration
SuperNEMO R&D
CENBG Bordeaux, France
IReS Strasbourg, France
LAL Orsay, France
LPC Caen, France
LSCE Gif sur Yvette, France
FNSPE Prague Univ., Czech Rep.
ITEP Moscow, Russia
JINR Dubna, Russia
Kurchatov Inst. Moscou, Russia
Karkhov Ukraine
Manchester University, UK
UCL London, UK
INL Idaho Falls, USA
MHC Massachusets , USA
Saga Univ., Japan
Texas Univ. Austin, USA
Source
Calorimeter
Drift Chamb
Radiopurity
Electronics
Computing
Enrichment
Scintillators
Prototype
HPGe spectr
Calorimeter
Simulation
Purification
PMT
Autom. wiring
BiPo det.
Drift chamb
Radon det.
Trigger
Foils prod.
Mechanics
© S. Julian, LAL
Possible contribution of Polish group:
• NEMO-3
- data analysis
• SuperNEMO
- modeling and simulations
- main detector design and construction
- data analysis
- detector for purity control of drift chamber gas
Detector for purity control of drift chamber gas
a possibility: Optical Time Projection Chamber
gas
drift
1 ms/cm
a
e
amp.
WLS
CCD
PMT
M. Ćwiok et al., IEEE TNS, 52 (2005) 2895
Performance of the OTPC
a
13O
p
K. Miernik et al.
Full detector
20 modules: 100 kg of enriched isotope
Needed cavity:
~60 x 15 x 15 m
Location:
14 m
Modane,
Gran Sasso …?
Source foil
Water shield ( 2 ktons)
3,75 m
© S. Julian, LAL
bb sources in the NEMO-3 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
Qbb = 2995 keV
bb0n search
100Mo
0.932 kg
natTe
491 g
Cu
621 g
External bkg
measurement
(all enriched isotopes produced in Russia)
purified in INL (USA) and ITEP (Russia)