Results from the NEMO 3 Experiment

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Results from the NEMO 3 Experiment

• Ladislav VÁLA
• Institute of Experimental and Applied Physics
• Czech Technical University in Prague

10th ICATPP Conference, 8 12 October 2007,
Villa Olmo, Como, Italy
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Outline

• Introduction bb decay
• NEMO 3 description
• NEMO 3 results
• Summary

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Introduction
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Double beta decay
In even-even nuclei where single b- decay is
highly suppressed or forbidden but b-b- decay is
possible, e.g. 48Ca, 76Ge, 82Se, 96Zr,
100Mo,116Cd, 130Te, 136Xe, 150Nd,
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Double beta decay
Neutrinoless bb decay (0nbb) (A,Z) ? (A,Z2)
2 e-
bb with Majoron emission (0ncbb) (A,Z) ?
(A,Z2) 2 e- c
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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 experimental approach
Calorimetry plus
tracking Detection of both electrons
reject unknown nuclear gamma lines Three
kinematic observables study underlying physics
mechanism (i) individual electron energies
(ii) angular correlation (iii) energy
sum Sources separated from the detector
measure T1/2 for several
isotopes Background rejection through particle
identification e, e, g, a
particles Unique
and complementary
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NEMO 3 detector
NEMO Neutrino Ettore Majorana Observatory
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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cathode rings (wire chamber)
iron shielding
water tank
PMT
scintillators
bb isotope foils
calibration tube
coil
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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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Radon trapping facility
Phase I February 2003 September 2004 (radon
background in data) 1 0nbb-like event/y/kg
with 2.8 lt E1E2 lt 3.2 MeV
Phase II since October 2004 (radon level
reduced by a factor of 10)
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
Bi-Po process
Inside the NEMO 3 tent factor of 100
300 Inside NEMO 3 factor of 10 A(222Rn) ? 2
mBq/m3
Radon background for 0nbb search is then
negligible for Phase II
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bb event from data
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NEMO 3 results
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2nbb decay of 100Mo
Phase I data (February 2003 October 2004) with
radon
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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2nbb decay of 82Se
Phase I data (February 2003 October 2004) with
radon
T1/2 9.6 0.3 (stat) 1.0 (syst) ? 1019
y Phys. Rev. Lett. 95 (2005) 182302
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2nbb decay of 116Cd, 150Nd, 96Zr, 48Ca
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 48Ca T1/2 3.9 0.7 (stat) 0.6
(syst) ? 1019 y
Additional statistics are being analysed and will
be published soon
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2nbb decay of 130Te
background subtracted
Preliminary result 130Te T1/2 7.6 1.5
(stat) 0.8 (syst) ? 1020 y
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bb decay to exc. states 100Mo
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. Nucl.
Phys. A 781 (2007) 209
Clear topology 01 2e- 2g in time energy
and TOF cuts 21 2e- 1g in time energy and
TOF cuts
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0nbb decay of 100Mo
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 (0.8 1.3) eV 1-3 VA T1/2 gt
3.2 1023 y _at_ 90 C.L. ?l? lt 1.6 10-6 4
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0nbb decay of 82Se
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 (1.4 2.2) eV 1-3 VA T1/2 gt 1.2
1023 y _at_ 90 C.L. ?l? lt 2.8 10-6 5
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0nbb decay search
Collaboration decided to perform blind analysis
with mock data. Plan to open the box and update
the results summer 2008 and once again at the
end of the experiment early 2010.

• expected limits in 2009
• 100Mo
• T1/2(0???) gt 2 1024 y (90 CL)
• ?mn? lt (0.4 0.7) eV
• 82Se
• T1/2(0???) gt 8 1023 y (90 CL)
• ?mn? lt (0.7 1.1) eV

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0n?bb decay
Neutrinoless bb decay with Majoron emission (A,Z)
? (A,Z2) 2e- c0 (c0)
334.3 days of data (Phase I)
100Mo T1/2 gt 2.7 1022 y _at_ 90 C.L. ?gee? lt
(0.5 1.9) 10-4
82Se T1/2 gt 1.5 1022 y _at_ 90 C.L. ?gee? lt (0.7
1.7) 10-4
Nucl. Phys. A 765 (2006) 483.
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Summary
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Summary
NEMO 3 unique approach combining tracking and
calorimetry
No signal seen for 0nbb decay Half-life limits
for 100Mo and 82Se T1/2 (100Mo) gt 5.8 1023 y
T1/2 (82Se) gt 2.1 1023 y Best limits for 0ncbb
decay of 100Mo and 82Se
2nbb decay of 100Mo and 82Se measured with high
statistics Preliminary results for 2nbb for the
other 5 isotopes (analysis of Phase II data in
progress, to be published soon)
New measurement and T1/2 limits for bb decay of
100Mo to excited states
SuperNEMO RD programme under way (see the talk
of Irina Nasteva)
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Thank you for your attention
NEMO/SuperNEMO Collaboration Meeting, July 2007,
Manchester
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Backup slides
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Background measurement
NEMO 3 can measure each component of its
background!
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2nbb decay of 130Te

• The 2??? half-life of 130Te has been a
  long-standing mystery
• Geochemical
• (25 2) 1020 years (Kirsten 83)
• (27 2) 1020 years (Bernatowicz 93)
• (7.9 1) 1020 years (Takaoka 96)
• 8 x 1020 years (Manuel 91)
• Difference between old and young ores due to
• time dependence of constants?
• Using geochemical ratio of 82Se/130Te and
  present T1/2value for 82Se from direct
  experiments
• (9 1) 1020 years (average by A. Barabash)
• Direct measurement
• (6.1 1.4 (syst) 2.9 3.4) 1020 years
  (Arnaboldi 2003)