1. Neutrino Ettore Majorana Observatory
NEMO-3 Experiment
Neutrino Ettore Majorana Observatory
FIRST RESULTS
Dominique Lalanne *
for the
NEMO-3 Collaboration
CENBG, IN2P3-CNRS et Université de Bordeaux, France
Charles University, Praha, Czech Republic
CTU, Praha, Czech Republic
INEEL, Idaho Falls, USA
IReS, IN2P3-CNRS et Université de Strasbourg, France
ITEP, Moscou, Russia
JINR, Dubna, Russia
Jyvaskyla University, Finland
* LAL, IN2P3-CNRS et Université Paris-Sud, France
LSCE, CNRS Gif sur Yvette, France
LPC, IN2P3-CNRS et Université de Caen, France
Mount Holyoke College, USA
RRC Kurchatov Institute, Moscow, Russia
Saga University, Saga, Japon
UCL, London, Great-Britain
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

2. Measurement of bb2n decay for several nuclei
Outline of the talk:
NEMO-3 Detector
Measurement of bb2n decay for several nuclei
gives information on nuclear processes
(2 electron events of energy up to the Q value)
Search for bb0n decay with 100Mo and 82Se
if signal:
the neutrino is of Majorana type
measurement of the effective neutrino mass
(2 electron events of energy exactly the Q value)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

3. Fréjus Underground Laboratory : 4800 m.w.e.
The NEMO3 detector
3 m
4 m
B (25 G)
20 sectors
Fréjus Underground Laboratory : 4800 m.w.e.
Magnetic field: 25 Gauss
Gamma shield: Pure Iron (e = 18 cm)
Neutron shield: 30 cm water (ext. wall)
40 cm wood (top and bottom)
(since march 2004: water + boron)
Source: 10 kg of  isotopes
cylindrical, S = 20 m2, e ~ 60 mg/cm2
Tracking detector:
drift wire chamber operating
in Geiger mode (6180 cells)
Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O
Calorimeter:
1940 plastic scintillators
coupled to low radioactivity PMTs
Able to identify e-, e+, g and a
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

4. PMTs scintillators Cathodic rings Wire chamber Calibration tube
bb isotope foils
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

5. AUGUST 2001
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

6. Start taking data 14 February 2003
NEMO-3 Opening Day, July 2002
Start taking data 14 February 2003
Water tank
wood
coil
Iron shield
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

7. bb decay isotopes in NEMO-3 detector
bb2n measurement
116Cd g
Qbb = keV
96Zr g
Qbb = 3350 keV
150Nd g
Qbb = keV
48Ca g
Qbb = 4272 keV
130Te g
Qbb = 2529 keV
External bkg
measurement
100Mo kg
Qbb = 3034 keV
82Se kg
Qbb = 2995 keV
natTe g
Cu g
bb0n search
(All the enriched isotopes produced in Russia)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

8. bb events selection in NEMO-3
Deposited energy:
E1+E2= 2088 keV
Internal hypothesis:
(Dt)mes –(Dt)theo = 0.22 ns
Common vertex:
(Dvertex) = 2.1 mm
Vertex
emission
(Dvertex)// = 5.7 mm
Transverse view
Longitudinal
view
Run Number: 2040
Event Number: 9732
Date:
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)
bb events selection in NEMO-3
Typical bb2n event observed from 100Mo
Transverse view
Run Number: 2040
Event Number: 9732
Date:
Longitudinal
view
100Mo foil
100Mo foil
Geiger plasma
longitudinal
propagation
Drift distance
Scintillator
+ PMT
Trigger: PMT > 150 keV
3 Geiger hits (2 neighbour layers + 1)
Trigger rate = 7 Hz
bb events: 1 event every 1.5 minute
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

9. Expected Performance of the detector
Time Of Flight:
Time Resolution (bb channel)  250 ps at 1 MeV
ToF (external crossing e- ) > 3 ns
external crossing e- totaly rejected
External Background
bb events from the foil
(Dtmes – Dtcalc) external hypo. (ns)
(Dtmes – Dtcalc) internal hypo. (ns)
Calorimeter:
97% of the PMTs+scintillators are ON
Energy Resolution:
calibration runs (every ~ 40 days) with 207Bi sources
17%
14%
FWHM (1 MeV)
Int. Wall
3" PMTs
Ext. Wall
5" PMTs
207Bi
2 conversion e-
482 keV and 976 keV
482 keV
976 keV
FWHM = 135 keV
(13.8%)
Daily Laser Survey to control gain stability of each PM
gamma: efficiency ~ keV, Ethr = 30 keV
Tracking Detector:
99.5 % Geiger cells ON
Vertex resolution:
2 e- channels (482 and 976 keV) using 207Bi sources
at 3 well known positions in each sector
s (DVertex) = 0.6 cm
s// (DVertex) = 1.3 cm (Z=0)
e+/e- separation with a magnetic field of 25 G
~ 3% confusion at 1 MeV b-
DVertex
DVertex = distance between the two vertex
Expected Performance of the detector
has been reached
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

10. Measurement of 2b2n decay
in NEMO-3
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

11. 100Mo 22 preliminary results
(Data 14 Feb – 22 Mar. 2004)
Sum Energy Spectrum
Angular Distribution
NEMO-3
events
6914 g
241.5 days
S/B = 45.8
NEMO-3
events
6914 g
241.5 days
S/B = 45.8
100Mo
100Mo
Data
22
Monte Carlo
Data
Background
subtracted
22
Monte Carlo
Background
subtracted
E1 + E2 (keV)
Cos()
T1/2 = 7.72 ± 0.02 (stat) ± 0.54 (syst)  1018 y
4.57 kg.y
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

12. 100Mo 22 Single Energy Distribution HSD SSD
HSD, higher levels
contribute to the decay
SSD, 1+ level
dominates in the decay
(Abad et al., 1984,
Ann. Fis. A 80, 9)
100Mo 0+
100Tc 1+
Single electron spectrum different
between SSD and HSD
Simkovic,
J. Phys. G, 27, 2233, 2001
Esingle (keV)
NEMO-3
4.57 kg.y
E1 + E2 > 2 MeV
NEMO-3
4.57 kg.y
E1 + E2 > 2 MeV
Data
Data
22 SSD
Monte Carlo
22 HSD
Monte Carlo
HSD
higher levels
SSD
Single State
Background
subtracted
Background
subtracted
2/ndf = 139. / 36
2/ndf = 40.7 / 36
Esingle (keV) (for the electron of low energy in the pair)
Esingle (keV)
HSD: T1/2 = 8.61 ± 0.02 (stat) ± 0.60 (syst)  1018 y
SSD: T1/2 = 7.72 ± 0.02 (stat) ± 0.54 (syst)  1018 y
100Mo 22 single energy distribution
in favour of Single State Dominant (SSD) decay
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

13. 22 preliminary results for other nuclei
NEMO-3
932 g
241.5 days
2385 events
S/B = 3.3
Background subtracted
82Se
82Se T1/2 = 10.3 ± 0.2 (stat) ± 1.0 (syst)  1019 y
116Cd if SSD T1/2 = 2.8 ± 0.1 (stat) ± 0.3 (syst)  1019 y
if HSD T1/2 = 3.05 ± 0.1 (stat) ± 0.3 (syst)  1019 y
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
Data
bb2n
simulation
E1+E2 (keV)
NEMO-3
405 g
168.4 days
1371 events
S/B = 7.5
NEMO-3
37 g
168.4 days
449 events
S/B = 2.8
NEMO-3
5.3 g
168.4 days
72 events
S/B = 0.9
116Cd
150Nd
96Zr
Data
Data
Data
bb2n
simulation
bb2n
simulation
bb2n
simulation
E1+E2 (MeV)
E1+E2 (MeV)
E1+E2 (MeV)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

14. Search for 2b0n decay in NEMO-3
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

15. bb0n Analysis: Background Measurement
NEMO-3 can measure each component of its background !
External Background 208Tl (PMTs)
Measured with (e-, g) external events
~ 10-3 bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV
External Neutrons and High Energy gamma
Measured with (e-,e-)int events with E1+E2 > 4 MeV
 0.02 bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV ~
Only 2 (e-,e-)int events with E1+E2 > 4 MeV
observed after 260 days of data (without boron)
4253 keV (26 Mar. 2003)
6361 keV (8 Nov. 2003)
In agreement with expected background
< 110
92  18
100Mo metal.
400  100
316  46
82Se
< 100
115  13
100Mo comp.
A (mBq/kg)
HPGe meas.
from (e-, Ng)
sources
In agreement with HPGe measurements
208Tl impurities inside the foils
Measured with (e-,2g), (e-,3g) events coming from the foil
~ 0.1 bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV
100Mo bb2n decay T1/2 = y (SSD)
~ bb0n-like events year-1 kg -1 with 2.8<E1+E2<3.2 MeV
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

16. Radon is the dominant background today
bb0n Analysis: Background Measurement
Radon in the NEMO-3 gas of the wire chamber
Due to a tiny diffusion of the radon of the laboratory inside the detector
A(Radon) in the lab ~15 Bq/m3
Two independant measurements of radon in NEMO-3 gas
Good agreement between the two measurements
Radon detector at the input/output of the NEMO-3 gas
~ 20 counts/day for 20 mBq/ m3
(1e- + 1 a) channel in the NEMO-3 data:
Delayed tracks (<700 ms) to tag delayed a from 214Po
214Bi  214Po (164 ms)  210Pb
~ 200 counts/hour for 20 mBq/m3
A(Radon) in NEMO-3  mBq/m3
Decay
in gas b-
delayed a
222Rn (3.8 days)
218Po
214Pb
214Bi
214Po
210Pb b a
164 ms
~ 1 bb0n-like events/year/kg with 2.8 < E1+E2 < 3.2 MeV
Radon is the dominant background today
for bb0n search in NEMO-3 !!!
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

17. bb0n Analysis with 100Mo 100Mo Cu + natTe + 130Te 100Mo PRELIMINARY
6914 g
265 days
Data
bb2n
Monte-Carlo
Radon
E1+E2 (MeV)
bb0n arbitrary
unit
Cu + natTe + 130Te
265 days
Radon
Monte-Carlo
Data
E1+E2 (MeV) 8
11.4  3.4
____
2.6  0.7 2
2.6<E1+E2<3.2
2.8<E1+E2<3.2
100Mo
2.6<E1+E2<3.2
2.8<E1+E2<3.2
100Mo 2b2n M-C
32.3  1.9
1.4  0.2
Radon M-C
23.5  6.7
5.6  1.7
TOTAL Monte-Carlo
55.8  7.0
7.0  1.7
DATA 50 8
V-A: T1/2(bb0n) > y
V+A: T1/2 > y with E1- E2> 800 keV
Majoron: T1/2 > y with Esingle > 700 keV
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

18. 100Mo bb0n likelihood analysis
3 variables used for the likelihood
Ec1+ Ec2 sum of the kinetic energies of the 2 e-
Ecmin energy of the e- of minimal energy
Cos angle between the two tracks
Ec = Energy at the exit of the 100Mo foil
= Energy deposited in scintillator (E)
+ energy losses in the tracking detector ! b-
Cos
Ec1
Ec2 E1 E2
Nbb0n
xbb0n = is the free parameter
Ntot
L calculated with bb events Ec1+Ec2>2 MeV
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

19. 100Mo bb0n likelihood analysis
PRELIMINARY
100Mo bb0n likelihood analysis
Data
bb2n
Monte-Carlo
Radon
bb0n
T1/2 = y
100Mo
6914 g
216.4 days
4.10 kg.y
Ec1+Ec2 (keV)
Previous limit V-A: T1/2(bb0n) > y (Elegant V, Ejiri et al., 2001)
V-A: T1/2(bb0n) > y (90% C.L.)
V+A: T1/2 > y (90% C.L.)
-Log(Likelihood)
xbb0n =
Nbb0n
Ntot
Ec1+Ec2 (keV)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

20. 82Se bb0n likelihood analysis
PRELIMINARY
82Se
932 g
216.4 days
0.55 kg.y
82Se
932 g
216.4 days
0.55 kg.y
Data
bb2n
Monte-Carlo
Radon
Data
bb2n
Monte-Carlo
Radon
bb0n
T1/2 =
Ec1+Ec2 (keV)
Ec1+Ec2 (keV)
V-A: T1/2(bb0n) > y (90% C.L.)
V+A: T1/2 > y (90% C.L.)
Majoron: T1/2 > y (90% C.L.)
Previous limit V-A: T1/2(bb0n) > y
(NEMO-2) Arnold et al. Nucl. Phys. A636 (1998)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

21. Limit on the effective mass of the Majorana neutrino,
on Majoron and on V+A
Limits on T1/2 90% C.L.
Simkovic et al., Phys. Rev. C60 (1999)
Stoica, Klapdor, Nucl. Phys. A694 (2001)
Caurier et al., Phys. Rev. Lett (1996)
Limit on the Majorana neutrino effective mass
100Mo: T1/2(bb0n) > y
mn < 0.7 – 1.2 eV
82Se: T1/2(bb0n) > y
mn < 1.3 – 3.6 eV
Limit on Majoron
100Mo: T1/2 > y
 < (5.3 – 8.5) Simkovic (1999), Stoica (1999)
82Se: T1/2 > y
 < (0.7 – 1.6) Simkovic (1999), Stoica (2001)
Limit on V+A
100Mo: T1/2 > y
l < (1.5 – 2.0) Tomoda (1991), Suhonen (1994)
82Se: T1/2 > y
l < Tomoda (1991)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

22. Anti-Radon System in construction
Today Radon is the dominant
background for NEMO-3
Today: A(222Rn) in the LSM ~ 15 Bq/m3
Factor ~ 10 too high
May 2004
May 2004 : Tent surrounding the detector
September 2004 : Radon Trapping Factory
(SuperKamiokande-like)
Expected activity:
A(222Rn) ~ 0.2 Bq/m3
150 m3/h
500 kg -45oC
Expected Purification Factor ~ 100
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

23. NEMO-3 Expected sensitivity (with Radon purification)
Background :
External Background is negligible
Internal Background:
208Tl : 100 mBq/kg for 100Mo
300 mBq/kg for 82Se
214Bi : < 300 mBq/kg
~ 0.1 count kg-1 y -1 with 2.8<E1+E2<3.2 MeV
bb2n: T1/2 = y (SSD)
~ 0.3 count kg-1 y -1 with 2.8<E1+E2<3.2 MeV
5 years of data
6914 g of 100Mo T1/2(bb0n) > y (90% C.L.)
<mn> < 0.2 – 0.35 eV
932 g of 82Se T1/2(bb0n) > y (90% C.L.)
<mn> < – 1.8 eV
(conservative limit)
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004

24. SUMMARY NEMO-3 Detector running since 14 Feb. 2003
Expected performance of the detector has been reached !
2b2n preliminary results for 100Mo, 82Se, 96Zr, 116Cd and 150Nd
already more than b2n events collected
100Mo: in favour of Single State Dominance (SSD)
Preliminary T1/2(bb0n) limit (216.4 days of data):
100Mo (4.10 kg.y) T1/2(bb0n) > y  mn < 0.7 – 1.2 eV
82Se (0.55 kg.y) T1/2(bb0n) > y  mn < 1.3 – 3.6 eV
Level of backgound as expected (except Radon presently ~ 10 times too high)
Anti-Radon system operating this September 2004
Suppression factor ~ 100
Expected sensitivity in 5 years (with radon purification)
100Mo: T1/2(bb0n) > y <mn> < 0.2 – 0.35 eV
82Se: T1/2(bb0n) > y <mn> < – 1.8 eV
Dominique Lalanne for the NEMO-3 Collaboration ICHEP 2004 Beijing August 16-21, 2004