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Recent Results of the NEMO 3 Experiment
Ladislav VÁLACzech Technical University in Prague
NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy
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Outline
Double beta decay
NEMO 3 description
NEMO 3 results(2 & 0 & 0)
Conclusion
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IntroductionIntroduction
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Double beta decay
Two-neutrino decay (2): (A,Z)→(A,Z+2) + 2 e + 2e
0 & 0: L = 2 process
• Majorana neutrino ≡ and effective mass m
• Light neutrino exchange → m
• Right-handed (V+A) current in weak interaction
→ m,
• Majoron emission → gM
• SUSY particle exchange →
with Majoron emission (0): (A,Z)→(A,Z+2) + 2 e +
Neutrinoless decay (0): (A,Z)→(A,Z+2) + 2 e
Wn
n
p
p
e
e
M
W
eR
eL
h
h
0
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Neutrinoless Double Beta Decayar
bit
rary
un
its
(Q ~ MeV)
Two electron energy spectrum
T02/1
Experimental signature:2 electronsE1 +E2 = Q
0 = (T1/2)-1 = G0(Q5,Z) |M0|
2 m2
G0 – phase space factor M – nuclear matrix elementm – effective neutrino mass
m = | j |Uej|2 eij mj |
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NEMO 3 description
NEMO 3 description
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NEMO 3 Collaboration
CEN Bordeaux-Gradignan, FranceCharles University, Prague, Czech Republic
Czech Technical University, Prague, Czech RepublicINEEL Idaho Falls, USA
INR Moscow, RussiaIReS Strasbourg, France
ITEP Moscow, RussiaJINR Dubna, Russia
Jyväskylä University, FinlandLAL Orsay, France
LSCE Gif-sur-Yvette, FranceLPC Caen, France
University of Manchester, United KingdomMount Holyoke College, USA
Kurchatov Institute, Moscow, RussiaSaga University, Japan
University College London, United Kingdom
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B (25 G)
4 m
20 sectors
3 m
6 m
6 m
Detector located in the Fréjus Underground Laboratory, France (4800 m.w.e.)
Source: 10 kg of isotopes, cylindrical, S = 20 m2, foils ~ 60mg/cm2
Tracking detector: drift wire chamber operating in Geiger mode(6180 cells)gas = 94% He + 4% ethyl alcohol + 1% Ar + 0.1% H2O
Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTsMagnetic field: 25 GaussGamma shield: pure iron (18 cm layer)Neutron shield: borated water (ext. wall, 30 cm layer) & wood (top and bottom, 40 cm layer)
NEMO 3 detector
identification of e–, e+, and -particles
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116Cd 405 gQ = 2805 keV
96Zr 9.4 gQ = 3350 keV
150Nd 37.0 gQ = 3367 keV
48Ca 7.0 gQ = 4272 keV
130Te 454 gQ = 2529 keV
natTe 491 g
Cu 621 g
2 decaymeasurement
External background measurement
100Mo 6.914 kgQ = 3034 keV 0 decay search82Se 0.932 kg
Q = 2995 keV&
NEMO 3 sources
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event from data
Deposited energy: E1 + E2= 2088 keVInternal hypothesis: (t)mes – (t)theo = 0.22 nsCommon vertex: (vertex) = 2.1 mm (vertex)// = 5.7 mm
Run Number: 2040Event Number: 9732Date: 2003-03-20
100Mo foils
Scintillator+ PMT
Longitudinal viewTransverse view
Vertex of the ee emission
Vertex of the ee emission
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External background 208Tl (PMTs) Measured with (e) external events~ 10-3 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV
~ 0.1 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV
208Tl impurities inside the foils Measured with (e2), (e3) events coming from the foil
External neutrons and high energy ’s Measured with (ee)int events with E1+E2 > 4 MeV
0.02 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV
NEMO 3 can measure each component of its background!
100Mo 2 decay T1/2 = 7.1 × 1018 y ~ 0.3 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV
Background measurement
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Radon background
~ 1 0-like event/y/kg with 2.8 < E1+E2 < 3.2 MeV
Radon was the dominant background forthe 0 search in the NEMO 3 Phase I data !!!
Radon was the dominant background forthe 0 search in the NEMO 3 Phase I data !!!
Radon in the NEMO 3 gas of the wire chamber
Due to a tiny diffusion of the radon of the laboratoryinside the detector: A(Rn) in the lab ~15 Bq/m3
Two independent measurements of
radon in the NEMO 3 gas
Good agreement between the two measurements
1. Radon detector at the input/output of the NEMO 3 gas
2. (1e + 1) channel in the NEMO 3 data
A(Rn) inside NEMO 3 20-30 mBq/m3 (Phase I)
222Rn (3.8 days)
218Po
214Pb
214Bi
214Po
210Pb
s
Decay inthe gas
delayed
214Bi → 214Po (164 s) → 210Pb
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Radon trapping facility
Start-up: October 4th 2004
1 ton of charcoal @ –50oC, 9 barsair flux = 150 m3/h
Input: A(222Rn) 15 Bq/m3
Output: A(222Rn) < 15 mBq/m3 !!!reduction factor of 1000
NEMO 3 tent: factor of 100 – 300
inside NEMO 3: factor of 10A(222Rn) 2 mBq/m3
February 2003 – September 2004: Phase I (radon background in data)Since October 2004: Phase II (radon level reduced by a factor of 10)
Radon backgroundis negligible today!
Radon backgroundis negligible today!
0.015 Bq/m3
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Radon trapping facility
chilling unit
charcoal columns
compressorbuffer
dryer
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NEMO 3 results
NEMO 3 results
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100Mo: 2 decay
T1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ] 1018 y
Phys. Rev. Lett. 95 (2005) 182302
T1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ] 1018 y
Phys. Rev. Lett. 95 (2005) 182302
219 000 events6914 g
389 daysS/B = 40
cos(ee)
Data2 MCsimulation
Background subtracted
Sum Energy Spectrum Angular Distribution
Data2 MCsimulation
Background subtracted
219 000 events6914 g
389 daysS/B = 40
E1 + E2 (MeV)
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2 HSDMC simul.
Background subtracted
• Data
Esingle (keV)
HSD
2/ndf = 139./36
Esingle (keV)
2 HSDMC simul.
Background subtracted
• DataSSD
2/ndf = 40.7/36
Single electron energy distribution of the 2 decayof 100Mo in favor of Single State Dominance (SSD) model
Single electron energy distribution of the 2 decayof 100Mo in favor of Single State Dominance (SSD) model
Single electron spectrumdifferent between SSD and HSD
Šimkovic et al., J. Phys. G 27 (2001) 2233.
Esingle (keV)
HSD, higher levels contribute to the decay
SSD, 1+ level dominates in the decayAbad et al., Ann. Fis. A 80 (1984) 9.
100Mo
0+
100Tc
1+
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100Mo: decay to exc. states
2 decay to the 01+ state: S/B = 3.0
T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y
0 decay to the 01+ state:
T1/2 > 8.9 1022 y @ 90 % C.L.
2 decay to the 21+ state:
T1/2 > 1.1 1021 y @ 90 % C.L.
0 decay to the 21+ state:
T1/2 > 1.6 1023 y @ 90 % C.L.
To be published soon, submitted to Nucl. Phys. A
2 decay to the 01+ state: S/B = 3.0
T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y
0 decay to the 01+ state:
T1/2 > 8.9 1022 y @ 90 % C.L.
2 decay to the 21+ state:
T1/2 > 1.1 1021 y @ 90 % C.L.
0 decay to the 21+ state:
T1/2 > 1.6 1023 y @ 90 % C.L.
To be published soon, submitted to Nucl. Phys. A
Clear topology:
01+: 2e- + 2 in time & energy and TOF cuts
21+: 2e- + 1 in time & energy and TOF cuts
100Mo
0+
21+ (540 keV)
01+ (1130 keV)
41+ (1227 keV)
0+ (g.s.)100Ru
22+ (1362 keV)
303
4 k
eV
1
2
334.3 days of data (Phase I)
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100Mo: 0 decay
Energy window: 2.78 MeV < Eee < 3.20 MeV
14 events observed, 13.4 events expected
7.9 events excluded at 90% C.L.
V-A: T1/2 > 5.8 × 1023 y @ 90% C.L.
m < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4]
V+A: T1/2 > 3.2 × 1023 y @ 90% C.L.
< 1.6 × 10-6 [5]
Energy window: 2.78 MeV < Eee < 3.20 MeV
14 events observed, 13.4 events expected
7.9 events excluded at 90% C.L.
V-A: T1/2 > 5.8 × 1023 y @ 90% C.L.
m < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4]
V+A: T1/2 > 3.2 × 1023 y @ 90% C.L.
< 1.6 × 10-6 [5]
693 days of dataPhase I + Phase II
[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.[5] J.Suhonen et al., Nucl.Phys. A 700 (2002) 649.
NM
E:
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T1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ] 1019 y
Phys. Rev. Lett. 95 (2005) 182302
T1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ] 1019 y
Phys. Rev. Lett. 95 (2005) 182302
2750 events932 g
389 daysS/B = 4
Sum Energy Spectrum
Data2 MCsimulation
Background subtracted
E1 + E2 (MeV)
82Se: 2 decay
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82Se: 0 decay
Energy window: 2.62 MeV < Eee < 3.20 MeV
7 events observed, 6.4 events expected
6.2 events excluded at 90% C.L.
V-A: T1/2 > 2.1 × 1023 y @ 90% C.L.
m < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4]
V+A: T1/2 > 1.2 × 1023 y @ 90% C.L.
< (2.8 – 3.0) × 10-6 [6]
Energy window: 2.62 MeV < Eee < 3.20 MeV
7 events observed, 6.4 events expected
6.2 events excluded at 90% C.L.
V-A: T1/2 > 2.1 × 1023 y @ 90% C.L.
m < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4]
V+A: T1/2 > 1.2 × 1023 y @ 90% C.L.
< (2.8 – 3.0) × 10-6 [6]
693 days of dataPhase I + Phase II
[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.[6] M.Aunola et al., Nucl.Phys. A 463 (1998) 207.
NM
E:
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Preliminary results:116Cd: T1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ] 1019 y (SSD)
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
Preliminary results:116Cd: T1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ] 1019 y (SSD)
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
116Cd, 150Nd, 96Zr: 2 decay
E1+E2 (MeV) E1+E2 (MeV) E1+E2 (MeV)
116Cd 150Nd 96Zr
2simul.
Data
2simul.
Data
2simul.
Data
818 events37 g
365.4 daysS/B = 2.4
2348 evts405 g
365.4 daysS/B = 7.6
127 events 5.3 g
365.4 daysS/B = 0.9
Background subtracted
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48Ca: 2 decay
Preliminary result:
48Ca: T1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ] 1019 y
Preliminary result:
48Ca: T1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ] 1019 y
40 events 7.0 g
466.7 daysS/B = 15.7
Very smallbackground!
Phase I + Phase II data
Ee > 0.7 MeV&
cos(ee) < 0
E1+E2 (MeV)
48Ca
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0 decay
Netrinoless decay with Majoron emission
(A,Z) → (A,Z+2) + 2e + 0
[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica and H.V. Klapdor-Kleingrothaus, Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese and J.Suhonen, Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.
NM
E:
100Mo:
T1/2 > 2.7 × 1022 y @ 90% C.L.
gee < (0.5 – 1.9) × 10-4
100Mo:
T1/2 > 2.7 × 1022 y @ 90% C.L.
gee < (0.5 – 1.9) × 10-4
82Se:
T1/2 > 1.5 × 1022 y @ 90% C.L.
gee < (0.7 – 1.7) × 10-4
82Se:
T1/2 > 1.5 × 1022 y @ 90% C.L.
gee < (0.7 – 1.7) × 10-4
Nucl. Phys. A 765 (2006) 483.
334.3 days of data (Phase I)
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ConclusionConclusion
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New measurement and T1/2 limits for decay of 100Mo to
excited states
Conclusion
No signal seen for 0 decay
Improved limits:
100Mo: T1/2 > 5.8 × 1023 y, m < (0.6 – 2.7) eV
82Se: T1/2 > 2.1 × 1023 y, m < (1.2 – 3.2) eV
Improved limits for 0 decay of 100Mo and 82Se
2 decay of 100Mo and 82Se measured with high statistics
Preliminary results for other isotopes
Analysis of Phase II data in progress
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Spare Slides About
SuperNEMO
Spare Slides About
SuperNEMO
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SuperNEMOSuperNEMO
Ladislav VÁLACzech Technical University in Prague
NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy
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extension of the NEMO 3 technique 100–200 kg of isotopes, thin source between
tracking volumes, surrounded by calorimeter.
sensitivity T1/2(0) > 1026 y, m < 50 meV
main improvements needed: energy resolution (FWHM @ 3 MeV = 4%) detection efficiency (factor of 2) source radio purity (factor of 10) background rejection methods
SuperNEMO Project
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NEMO collaboration + new labs ~ 60 physicists, 11 countries, 27 laboratories
USAMHCINL
(U. Texas)
JapanU. Saga
U. Osaka
FranceCEN Bordeaux
IReS StrasbourgLAL OrsayLPC Caen
LSCE Gif/Yvette
UKUC London
U ManchesterIC London
FinlandU. Jyväskylä
RussiaJINR DubnaINR MoscowITEP Moscow
Kurchatov Institute
UkraineINR Kiev
ISMA Kharkov
Czech RepublicCharles U. Prague
CTU Prague
MaroccoFes U.
SlovakiaU. Bratislava
SpainU. ValenciaU. Zarogoza
U. Autonoma Barcelona
SuperNEMO Collaboration
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14 m
3 m
For each module:Calorimeter : 300 to 1000 PMT’s(depending on the final design)Resolution (FWHM) at 3 MeV = 4%
Tracking : drift chamber (3000 cells in Geiger mode)
Magnetic field : 25 gauss
Water shield: 2kT of water for 20 modules
Source foil: 5 kg of enriched 150Nd or 82Se
Number of modules = 20
(0) ~ 30 %
Possible Design
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Goal : T1/2 1026 y m 50 meV
The best choice for phase space and background
Q = 3.367 MeV150Nd
Radiopurity requirements for the source
208Tl < 2 Bq/kg
T2 = 9 x1018 y Expected background from 2 = 2.2 evt/500kg.y in 200 keV
Enrichment by laser (200 keV energy window at Q)
Phase space factor G0 = 8.00 x 10-25 y-1eV-2
Sources = G M m2
T1 2
Q = 2.995 MeV Phase space factor G0 = 1.08 x 10-25 y-1eV-282Se
T2 = 9 x 1019 y Expected background from 2 = 1.4 evt/500kg.y in 200 keV
Enrichment by ultracentrifugation
214Bi < 10 Bq/kg208Tl < 2 Bq/kg Rn < 2 Bq/m3
Radiopurity requirements for the source
(200 keV energy window at Q)