Prsentation PowerPoint

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Journées Neutrinos 27-28 novembre 2003
LPNHE-Paris
NEMO Experiment Neutrino Ettore Majorana
Observatory

• NEMO-3 Detector
• Preliminary results
• Performance of the detector
• 2b2n analysis for 100Mo, 82Se and 150Nd
• Background study for 2b0n research (208Tl and
  Radon)
• Future of NEMO

Xavier Sarazin for NEMO Collaboration
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NEMO Experiment Neutrino Ettore Majorana
Observatory

• Search for neutrinoless double beta decay
• Study several isotopes
• Mo100 , Se82 , Te130 , Cd116 , Zr96 , Ca48 ,
  Nd150
• Tag and measure all the components of background
• e-, e, g, a, neutrons

zero background experiment
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Double beta bb(0n) decay Physics beyond the
standard model

• DL 2 Process
• Majorana Neutrino n n and effective mass ltmngt
• Right-handed current in weak interaction
• Majoron emission
• SUSY particle exchange

bb(0n) 2n ? 2p2e-
p
n
W-
e-
neR
h
nM
neL
h
e-
W-
n
p
(Qbb MeV)
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Located in Modane Underground Laboratory

• Sources 20 m2, total mass 10 kg, thickness
  60 mm
• Tracking detector (6180 Geiger cells in
  Healcohol) Vertex st 5 mm, sz 1 cm
• Calorimeter (1940 plastic scintillators
  PMTs low radioactivity) sE/E 3 at 3 MeV
• g and neutron shield Iron shield (18 cm)
  water shield wood shield parafin
• magnetic field B25 G
• all materials low radioactivity (total
  activity in 208Tl and 214Bi ? 300 Bq)

1 sector of NEMO3
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Cathodic rings Wire chamber
PMTs
Calibration tube
scintillators
bb isotope foils
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AUGUST 2001
June 2002 tests runs February 2003 beginning
of data taking
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wood
coil
Iron shield
Water tank
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Sources preparation
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Sources in NEMO-3 detector
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Expected background and sensitivity
5 years of data Energy window 2.8-3.2
MeV Efficiciency bb0n 14
External and neutron background negligeable
1 kg of 82Se
7 kg of 100Mo
Source contamination A(214Bi) lt 0.3 mBq/kg
A(208Tl) lt 0.02 mBq/kg Internal background
214Bi lt 0.04 evts/y/kg 208Tl lt 0.04
evts/y/kg bb(2n) 0.11 evts/y/kg
Source contamination A(214Bi) 1.2?0.5 mBq/kg
(measured) A(208Tl) 0.4?0.1 mBq/kg Internal
background bb(2n) 0.01 evts/y/kg
Hot spots Pollution rejected
Total Bkg lt 1.4 event/year T1/2(0n) gt 8.1024
y ltmngt lt 0.1 0.3 eV
Bkg 0 event/year T1/2(0n) gt 1.5.1024 y ltmngt lt
0.6 1.2 eV
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• NEMO-3 Preliminary Results
• Performance of the detector
• bb2n analysis for 100Mo, 82Se, 150Nd
• Background analysis for bb0n search

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Data Tacking
October 1st 2003 161 days of data tacking 75
efficiency
Trigger 1 PM gt 150 keV 3 Geiger
hits (2 neighbour layers 1) Counting rate
7.5 Hz
Proportion of types of events in raw data
Days of data collecting / month
Efficiency of data collecting / month
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Tracking Detector Performances

• 0.5 Geiger cells OFF
• 97.5 Geiger cells with 2 cathodic signals
• Longitudinal propagation of Geiger plasma
• Efficiency gt 93 for 90 of Geiger cells

RAW DATA
PROCESSED DATA
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Transversal and Longitudinal Resolution on the
Vertex
207Bi sources at 3 well known positions in each
sector (emission of two e- conversion at ? 1 and
0.5 MeV)
1 e- channel at 1 Mev s? (1 MeV) 0.2 cm
s// (1 MeV) 0.7 cm (Z0) 2e- channel (1
MeV 0.5 MeV) s? (1 MeV) 0.6 cm s// (1
MeV) 1.8 cm (Z0)
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Performances of the calorimeter
Tube in each sector where calibration sources are
introduced (3 positions) 3 electron energies
486 keV and 976 keV with 207Bi, and 2.28 MeV with
90Sr
At 1 MeV (Qbb?3 MeV for 100Mo and 82Se)
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bb2n EVENT OBSERVED BY NEMO-3
E1E2 2088 keV (Dt)mes (Dt)theo 0.22
ns (Dvertex)? 2.1 mm (Dvertex)// 5.7 mm
bb2n event
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100Mo 2?2? preliminary results
(14 Feb. 2003 30 Sep. 2003)
NEMO 3
Background substracted
2?2? Monte Carlo
160 days 75535 events
S/B 40
S/B(gt 1 MeV) ? 100
T1/2 7.8 0.09 (stat) 0.09 (syst) ? 1018 y
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100Mo 2?2? Single Energy Distribution
Calculations for 100Mo (Simkovic, J. Phys. G,
27, 2233, 2001)
Effect in one electron spectrum
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100Mo 2?2? angular distribution
Background substracted
NEMO 3
2?2? Monte Carlo
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82Se 2?2? preliminary results
(14 Feb. 2003 30 Sep. 2003)
Background substracted
2?2? Monte Carlo
3834 hours 1100 events S/B 4.2
Contaminated with low energy ?-emitters
Cuts E gt 300 keV Cos (?) lt 0.7
T1/2 9.52 0.25 (stat) 0.9 (syst) ? 1019 y
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150Nd 2?2? preliminary results
(June 2002 30 Sep. 2003)
Background substracted
2?2? Monte Carlo
3834 hours 400 events S/B 4.2
T1/2 7.5 0.3 (stat) 0.7 (syst) ? 1018 y
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Origin of Background at high energy
Two natural isotopes which have the greatest Qb
values gt 3 MeV 214Bi Qb ? 3.27 MeV 208Tl
Qb ? 4.99 MeV Design NEMO-3 detector for 10
kg 214Bi in source foils lt 0.3 mBq/kg
208Tl in source foils lt 0.02 mBq/kg Total
activity of the detector (200 tons) ? 300 Bq
In the Modane Underground Laboratory Fast
neutron flux (? 1 MeV) 3.5 1.5
10-6 n.cm-2s-1 Thermal neutron flux
(0.025 eV) 1.6 0.1 10-6 n.cm-2s-1
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How NEMO-3 tags the background

• Electron
• Gamma 50 efficiency at 1 MeV
• Energy Threshold 30 keV
• Time of Flight Time Resolution ? 250 ps at 1
  MeV
• e/e- separation with a magnetic field of 25 G
• 3 confusion at 1 MeV
• Delayed tracks (lt700 ms) to tag delayed a from
  Bi207
• 214Bi ? 214Po (164 ms) ? 210Pb

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Measurement of the sources of background
channels e- g s with Eg 2.6 MeV 212Bi ?
212Po e- (g) a T1/2(a)300 ns
208Tl
neutrons, external gammas
e- crossing, ee-, e-e- gt 4 MeV
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BACKGROUND EVENTS OBSERVED BY NEMO-3
Electron a delay track (164 ms) 214Bi ? 214Po
? 210Pb
Electron crossing gt 4 MeV Neutron capture
?
Electron positron pair B rejection
Electron N gs 208Tl (Eg 2.6 MeV)
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Search for 208Tl background in the foils
look for eg, e2g, e3g events coming from the foil
3800 h of data analysed 14 Feb. 2003 30 Sep.
2003 Tl cuts E?1 gt 400 keV E?2
gt 1900 keV E? gt 200 keV MC
?(Mo) 0.16 3.4 Rn events (3800 h.)
for 20 sectors
VERY PRELIMINARY Good agreement with the HPGe
measurements
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Neutron and High-Energy gamma Background
look for e-e- events gt 4 MeV coming from the foil
Only 1 bb0n-like event gt 4 MeV detected after 160
days of data tacking ! (14 Feb. 2003 30 Sep.
2003)
Run 2058 event 345966 26 March 2003 130Te source
(sector 19) E1E2 4448 keV
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Radon in NEMO-3
222Rn

• Two different measurements of radon in the NEMO-3
  gas
• Radon detector
• sensitivity 1 count/day for 1 mBq/m3
• Radon measurement ? 20 mBq/m3
• (1e- 1 a) channel in the NEMO-3 data
• Able to measure Radon every half day
• Radon measurement ? 30 mBq/m3

214Po
218Po
b
a 164 ms
214Bi
210Pb
214Pb
a few bb0n-like events due to radon, expected
in 1 year !!! TOO HIGH !!!

• A free Radon Tent surrounding the NEMO-3 detector
  in construction
• February 2004 200 kg Charcoal
• Factor 8 for Radon purification
• Spring 2004 Full Radon purification system
• Factor 100

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a bb0n-like event due to Radon from the gas
a track (delay 70 ms) 214Po ? 210Pb

• 214Bi ? 214Po
• decay
• IN THE GAS

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Free-Radon Purification System
Today A(222Rn) in the LSM 10 Bq/m3
Fall 2003 Tent surrounding the
detector A(222Rn) Bq/m3
Spring 2004 Radon-free Gas Facory A(222Rn)
0.2 Bq/m3 150 m3/h
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Sensitivity of NEMO3 to measure sources of
background
Design NEMO3 for 10 kg 208 Tl in source
foils lt 0.02 mBq/kg 214 Bi in source foils
lt 0.3 mBq/kg neutron flux lt 10-8 n cm-2 s-1

• Sensitivity NEMO3 after 2 years of data
• ? 208 Tl in source foils lt 2 mBq/kg
• channel eg s (Eg 2.6 MeV)
• 212 Bi ? 212 Po e(g)a (300 ns)
• ? 214 Bi in source foils lt 2 mBq/kg
• measured by channel e (g)  a
• ( 214 Bi ? 214 Po ? 210 Pb T1/2 164 ms )
• ? neutrons lt 10-9 n cm-2 s-1
• measured by e- crossing gt 4 MeV

Sensitivity to 100 kg of isotopes
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Future for a NEMO Detector Tracking-Calorimeter
Technique
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Expected values of ltmngt from neutrinos
oscillations parameters
Pascoli and Petcov, hep-ph/0310003 (best fit natm
nsol )
Quasi-Degenerate (QD) ltmngt gt 0.6 eV

Inverted Hierarchie (IH) 0.015 eV lt ltmngt lt
0.6 eV


Normal Hierarchie (NH) ltmngt lt 5. 10-3 eV

Next Generation of NEMO detector  detect  1
gold event/year with ltmngt 20 meV
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Future of NEMO
Number of bb0n event detected / year
N Avogadro A atomic mass M mass (g) of bb
enrich. Isotope e detection efficiency
Goal of a next NEMO detector
Real measurement with 1 GOLD EVENT / YEAR
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Future of NEMO

• 3-4-5 December 2003 1st meeting for Future of
  NEMO
• Start working groups to prepare a design proposal
  for a future NEMO detector
• Advantage of a Calo-Tracking approach
• Can measure several isotopes
• Tag and measure all backgounds zero background
  experiment
• May detect  Gold events 
• Start with realistic 100 kg isotope module
• could be extended to 1 ton with several modules)
• Working groups
• RD Calorimeter
• RD Tracking
• Sources Enrichment (100Mo, 82Se, 150Nd)
• Purification sources
• Simulation
• Main challenges

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ENERGY RESOLUTION IS ONE OF THE MAIN
CHALLENGE Goal lt 0.1 bb2n event/year in the bb0n
energy window
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ILIAS European funding for bb0n research
IN2P3 (5 years)
NEMO people involved in ILIAS (5 years)

• JRA1 low bkg. techn. for Deep Underground
  Laboratories
• Links LSM and Boulby
• Develop. Ultra Low Bkg. Facility Big effort on
  Germanium
• Radon factory

300 kEuros

• JRA2 RD for next detectors
• RD for calorimeter (silicon, scintillators)
• 82Se 2 kg production, purification and source
  making (2004-2005)
• 150Nd enrichment study

300 kEuros

• N4 next generation of bb0n detectors
• NEMO-Next working groups and Proposal

60 kEuros
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New members already interested USA (Texas
University), UK (UCL), Japan (KEK)
NOUVEAUX COLLABORATEURS SONT LES BIENVENUS
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CONCLUSIONS

• NEMO-3 Detector running since 14 Feb. 2003
• Data tacking efficiency 75
• Performance of the detector has been reached !
• 2b2n preliminary results for 100Mo, 82Se and
  150Nd
• already more than 75.000 2b2n events
  collected
• Background study for 2b0n search
• 208Tl (e- Ng channel) good agreement with
  HPGe measurements
• Neutrons and High-energy g only 1 bb0n-like
  event gt 4 MeV !
• Radon 20-30 mBq/m3 inside the detector
• a few bb0n-like events/year expected Too
  high !
• Free radon purification system under
  construction
• Radon/8 in Feb. 2004
• Radon/50 in Spring 2004
• Future of NEMO First meeting 3-5 december 2003

Goal (dream ?) for Next NEMO be able to
detect  1 gold event/year with ltmngt 20 meV