Recent%20Results%20of%20the%20NEMO%203%20Experiment

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Recent Results of the NEMO 3 Experiment

• Ladislav VÁLA
• Czech 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
• (2nbb 0nbb 0ncbb)
• Conclusion

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Introduction
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Double beta decay
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Neutrinoless Double Beta Decay
G0n (T1/2)-1 G0n(Qbb5,Z) M0n2 ?mn?2
G0n phase space factor M nuclear matrix
element ?mn? effective neutrino mass ?mn?
Sj Uej2 eiaj mj
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NEMO 3 description
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NEMO 3 Collaboration
CEN Bordeaux-Gradignan, France Charles
University, Prague, Czech Republic Czech
Technical University, Prague, Czech
Republic INEEL Idaho Falls, USA INR Moscow,
Russia IReS Strasbourg, France ITEP Moscow,
Russia JINR Dubna, Russia Jyväskylä University,
Finland LAL Orsay, France LSCE Gif-sur-Yvette,
France LPC Caen, France University of Manchester,
United Kingdom Mount Holyoke College,
USA Kurchatov Institute, Moscow, Russia Saga
University, Japan University College London,
United Kingdom
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NEMO 3 detector
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 PMTs
Magnetic field 25 Gauss Gamma shield pure iron
(18 cm layer) Neutron shield borated water (ext.
wall, 30 cm layer) wood (top and bottom, 40 cm
layer)
identification of e, e, g and a-particles
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NEMO 3 sources
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 natTe 491 g Cu 621 g
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bb event from data
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Background measurement
NEMO 3 can measure each component of its
background!
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Radon background
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Radon trapping facility
February 2003 September 2004 Phase I (radon
background in data) Since October 2004 Phase II
(radon level reduced by a factor of 10)
Start-up October 4th 2004 1 ton of charcoal _at_
50oC, 9 bars air flux 150 m3/h Input A(222Rn)
15 Bq/m3 Output A(222Rn) lt 15 mBq/m3
!!! reduction factor of 1000 NEMO 3 tent factor
of 100 300 inside NEMO 3 factor of
10 A(222Rn) ? 2 mBq/m3
Radon background is negligible today!
0.015 Bq/m3
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Radon trapping facility
dryer
charcoal columns
chilling unit
buffer
compressor
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NEMO 3 results
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100Mo 2nbb decay
Sum Energy Spectrum
Angular Distribution
T1/2 7.11 0.02 (stat) 0.54 (syst) ?
1018 y Phys. Rev. Lett. 95 (2005) 182302
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(No Transcript)
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100Mo bb decay to exc. states
334.3 days of data (Phase I)
2nbb decay to the 01 state S/B 3.0 T1/2
5.71.3-0.9(stat) 0.8(syst)?1020 y 0nbb decay
to the 01 state T1/2 gt 8.9 ? 1022 y _at_ 90
C.L. 2nbb decay to the 21 state T1/2 gt 1.1 ?
1021 y _at_ 90 C.L. 0nbb decay to the 21
state T1/2 gt 1.6 ? 1023 y _at_ 90 C.L. To be
published soon, submitted to Nucl. Phys. A
Clear topology 01 2e- 2g in time energy
and TOF cuts 21 2e- 1g in time energy and
TOF cuts
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100Mo 0nbb decay
Energy window 2.78 MeV lt Eee lt 3.20 MeV 14
events observed, 13.4 events expected 7.9 events
excluded at 90 C.L. V-A T1/2 gt 5.8 1023 y _at_
90 C.L. ?mn? lt (0.6 0.9) eV 1-3, lt (2.1
2.7) eV 4 VA T1/2 gt 3.2 1023 y _at_ 90
C.L. ?l? lt 1.6 10-6 5
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.
NME
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82Se 2nbb decay
T1/2 9.6 0.3 (stat) 1.0 (syst) ? 1019
y Phys. Rev. Lett. 95 (2005) 182302
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82Se 0nbb decay
Energy window 2.62 MeV lt Eee lt 3.20 MeV 7 events
observed, 6.4 events expected 6.2 events excluded
at 90 C.L. V-A T1/2 gt 2.1 1023 y _at_ 90 C.L.
?mn? lt (1.2 2.5) eV 1-3, lt (2.6 3.2) eV 4
VA T1/2 gt 1.2 1023 y _at_ 90 C.L. ?l? lt (2.8
3.0) 10-6 6
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.
NME
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116Cd, 150Nd, 96Zr 2nbb decay
Background subtracted
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
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48Ca 2nbb decay
40 events 7.0 g 466.7 days S/B 15.7
Phase I Phase II data Ee gt 0.7 MeV cos(?ee)
lt 0
Very small background!
Preliminary result 48Ca T1/2 3.9 0.7
(stat) 0.6 (syst) ? 1019 y
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0n?bb decay
Netrinoless bb decay with Majoron emission (A,Z)
? (A,Z2) 2e- c0
334.3 days of data (Phase I)
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Conclusion
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Conclusion
No signal seen for 0nbb decay Improved
limits 100Mo T1/2 gt 5.8 1023 y, ?mn? lt (0.6
2.7) eV 82Se T1/2 gt 2.1 1023 y, ?mn? lt (1.2
3.2) eV Improved limits for 0ncbb decay of
100Mo and 82Se
2nbb decay of 100Mo and 82Se measured with high
statistics Preliminary results for other isotopes
New measurement and T1/2 limits for bb decay of
100Mo to excited states
Analysis of Phase II data in progress
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Spare Slides About SuperNEMO
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SuperNEMO
Ladislav VÁLA Czech Technical University in Prague
NOW2006, 9th 16th September 2006, Conca
Specchiulla, Italy
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SuperNEMO Project

• extension of the NEMO 3 technique
• 100200 kg of isotopes, thin source between
  tracking volumes, surrounded by calorimeter.
• sensitivity T1/2(0nbb) gt 1026 y, ?mn? lt 50 meV
• main improvements needed
• energy resolution (FWHM _at_ 3 MeV 4)
• detection efficiency (factor of 2)
• source radio purity (factor of 10)
• background rejection methods

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SuperNEMO Collaboration
NEMO collaboration new labs 60 physicists,
11 countries, 27 laboratories
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Possible Design
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bb Sources
The best choice for phase space and background