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NEMO-3 Experiment N eutrino E ttore M ajorana O bservatory FIRST RESULTS. Xavier Sarazin 1 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

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NEMO-3 Experiment N eutrino E ttore M ajorana O bservatory FIRST RESULTS

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Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

NEMO-3 Experiment

Neutrino Ettore Majorana Observatory

FIRST RESULTS

Xavier Sarazin 1

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

1 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

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

  • Plan of the talk:

  • NEMO-3 Detector

  • Measurement of bb2n decay for several nuclei

  • Search for bb0n decay with 100Mo and 82Se


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

20 sectors

B(25 G)

3 m

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)

4 m

Able to identify e-, e+, g and a

The NEMO3 detector

Fréjus Underground Laboratory : 4800 m.w.e.

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

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Cathodic rings

Wire chamber

PMTs

Calibration tube

scintillators

bb isotope foils

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

AUGUST 2001

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

NEMO-3 Opening Day, July 2002

Start taking data 14 February 2003

Water tank

wood

coil

Iron shield

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

bb2n measurement

bb0n search

bb decay isotopes in NEMO-3 detector

116Cd405 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

130Te454 g

Qbb = 2529 keV

External bkg

measurement

natTe491 g

100Mo6.914 kg

Qbb = 3034 keV

82Se0.932 kg

Qbb = 2995 keV

Cu621 g

(All the enriched isotopes produced in Russia)

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Transverse view

Run Number: 2040

Event Number: 9732

Date: 2003-03-20

Longitudinal

view

Vertex

emission

Vertex

emission

Drift distance

Deposited energy:

E1+E2= 2088 keV

Internal hypothesis:

(Dt)mes –(Dt)theo = 0.22 ns

Common vertex:

(Dvertex) = 2.1 mm

(Dvertex)// = 5.7 mm

  • Trigger: 1 PMT > 150 keV

  • 3 Geiger hits (2 neighbour layers + 1)

  • Trigger rate = 7 Hz

  • bb events: 1 event every 1.5 minutes

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: 2003-03-20

Longitudinal

view

100Mo foil

100Mo foil

Geiger plasma

longitudinal

propagation

Scintillator

+ PMT

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Calorimeter:

  • 97% of the PMTs+scintillators are ON

  • Energy Resolution:

    calibration runs (every ~ 40 days) with 207Bi sources

bb events from the foil

Ext. Wall

5" PMTs

Int. Wall

3" PMTs

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

FWHM (1 MeV)

14%

17%

b-

External Background

  • Daily Laser Survey to control gain stability of each PM

  • gamma: efficiency ~ 50 % @ 500 keV, Ethr = 30 keV

DVertex

976 keV

  • Time Of Flight:

  • Time Resolution (bb channel)  250 ps at 1 MeV

    ToF (external crossing e- ) > 3 ns

    external crossing e- totaly rejected

b-

207Bi

2 conversion e-

482 keV and 976 keV

Expected Performance of the detector

has been reached

DVertex = distance between the two vertex

FWHM = 135 keV

(13.8%)

(Dtmes – Dtcalc) internal hypo. (ns)

(Dtmes – Dtcalc) external hypo. (ns)

482 keV

Performance of the detector

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Measurement of 2b2n decay

in NEMO-3

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

  • Data

  • Data

100Mo 22 preliminary results

(Data 14 Feb. 2003 – 22 Mar. 2004)

Sum Energy Spectrum

Angular Distribution

145 245 events

6914 g

241.5 days

S/B = 45.8

145 245 events

6914 g

241.5 days

S/B = 45.8

NEMO-3

NEMO-3

100Mo

100Mo

22

Monte Carlo

Background

subtracted

22

Monte Carlo

Background

subtracted

Cos()

E1 + E2 (keV)

T1/2 = 7.72 ± 0.02 (stat) ± 0.54 (syst)  1018 y

4.57 kg.y

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

HSD, higher levels

contribute to the decay

  • Data

  • Data

1+

SSD, 1+ level

dominates in the decay

(Abad et al., 1984,

Ann. Fis. A 80, 9)

100Tc

0+

100Mo

100Mo 22 Single Energy Distribution

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

4.57 kg.y

E1 + E2 > 2 MeV

NEMO-3

22 SSD

Monte Carlo

22 HSD

Monte Carlo

SSD

Single State

HSD

higher levels

Background

subtracted

Background

subtracted

2/ndf = 40.7 / 36

2/ndf = 139. / 36

Esingle (keV)

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

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Data

Data

Data

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

NEMO-3

NEMO-3

37 g

168.4 days

449 events

S/B = 2.8

405 g

168.4 days

1371 events

S/B = 7.5

5.3 g

168.4 days

72 events

S/B = 0.9

96Zr

150Nd

116Cd

bb2n

simulation

bb2n

simulation

bb2n

simulation

E1+E2 (MeV)

E1+E2 (MeV)

E1+E2 (MeV)

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Search for 2b0n decay

in NEMO-3

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

  • 100Mo bb2n decay T1/2 = 7.7 1018 y (SSD)

~ 0.3 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)

  • ExternalNeutrons and High Energy gamma

  • Measured with (e-,e-)int events with E1+E2> 4 MeV

4253 keV (26 Mar. 2003)

6361 keV (8 Nov. 2003)

In agreement with expected background

 0.02 bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV

~

  • External Background 208Tl (PMTs)

  • Measured with (e-, g) external events

sources

A (mBq/kg)

from (e-, Ng)

A (mBq/kg)

HPGe meas.

  • 208Tl impurities inside the foils

  • Measured with (e-,2g), (e-,3g) events coming from the foil

100Mo metal.

92  18

< 110

100Mo comp.

115  13

< 100

~ 10-3bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV

~ 0.1 bb0n-like events year-1 kg -1 with 2.8<E1+ E2<3.2 MeV

82Se

316  46

400  100

In agreement with HPGe measurements

bb0n Analysis: Background Measurement

NEMO-3 can measure each component of its background !

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

222Rn (3.8 days)

a

b-

214Bi  214Po (164 ms)  210Pb

Two independant measurements of radon in NEMO-3 gas

214Po

218Po

b

  • 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

164 ms

214Bi

b-

Decay

in gas

210Pb

214Pb

delayed

a

Good agreement between the two measurements

A(Radon) in NEMO-3  20-30 mBq/m3

~ 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 !!!

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

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

PRELIMINARY

6914 g

265 days

100Mo

265 days

Cu + natTe + 130Te

Data

E1+E2 (MeV)

Data

bb2n

Monte-Carlo

Cu + natTe + 130Te

Radon

Monte-Carlo

Radon

Monte-Carlo

2.6<E1+E2<3.2

2.6<E1+E2<3.2

____

____

bb0n arbitrary

unit

11.4  3.4

2.6  0.7

11.4  3.4

2.6  0.7

8

2

E1+E2 (MeV)

bb0n Analysis with 100Mo

100Mo

2.6<E1+E2<3.2

2.6<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

55.8  7.0

7.0  1.7

TOTAL Monte-Carlo

DATA

50

8

V-A: T1/2(bb0n) > 3 1023 y

V+A: T1/2 > 1.8 1023 y with E1- E2> 800 keV

Majoron: T1/2 > 1.4 1022 ywith Esingle > 700 keV

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

b-

E1

Cos

Ec1

b-

Ec2

E2

100Mo bb0n likelihood analysis

  • 3 variablesused for the likelihood

  • Ec1+ Ec2sum of the kinetic energies of the 2 e-

  • Ecminenergy 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

!

Nbb0n

xbb0n= is the free parameter

Ntot

L calculated with bb events Ec1+Ec2>2 MeV

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

PRELIMINARY

100Mo

6914 g

216.4 days

4.10 kg.y

Data

-Log(Likelihood)

bb2n

Monte-Carlo

Radon

Monte-Carlo

Data

Nbb0n

bb2n

Monte-Carlo

xbb0n=

Ntot

Radon

Monte-Carlo

Ec1+Ec2 (keV)

bb0n

T1/2 = 3.5 1023

V-A: T1/2(bb0n) > 3.5 1023 y (90% C.L.)

V+A: T1/2 > 2.0 1023 y (90% C.L.)

Previous limit V-A: T1/2(bb0n) > 5.5 1022 y (Elegant V, Ejiri et al., 2001)

100Mo bb0n likelihood analysis

100Mo

6914 g

216.4 days

4.10 kg.y

Ec1+Ec2 (keV)

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Data

Data

bb2n

Monte-Carlo

bb2n

Monte-Carlo

Radon

Monte-Carlo

Radon

Monte-Carlo

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

Ec1+Ec2 (keV)

Ec1+Ec2 (keV)

V-A: T1/2(bb0n) > 1.9 1023 y (90% C.L.)

V+A: T1/2 > 1.0 1023 y (90% C.L.)

Majoron: T1/2 > 1.2 1022 y (90% C.L.)

Previous limit V-A: T1/2(bb0n) > 9.5 1021 y

(NEMO-2) Arnold et al. Nucl. Phys. A636 (1998)

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Limit on the Majorana neutrino effective mass

100Mo: T1/2(bb0n) > 3.5 1023 y

mn < 0.7 – 1.2 eV

82Se: T1/2(bb0n) > 1.9 1023 y

mn < 1.3 – 3.6 eV

Simkovic et al., Phys. Rev. C60 (1999)

Stoica, Klapdor, Nucl. Phys. A694 (2001)

Simkovic et al., Phys. Rev. C60 (1999)

Stoica, Klapdor, Nucl. Phys. A694 (2001)

Caurier et al., Phys. Rev. Lett. 77 1954 (1996)

Limit on Majoron

100Mo: T1/2 > 1.4 1022 y

 < (5.3 – 8.5) 10-5 Simkovic (1999), Stoica (1999)

82Se: T1/2 > 1.2 1022 y

 < (0.7 – 1.6) 10-4 Simkovic (1999), Stoica (2001)

Limit on V+A

100Mo: T1/2 > 2.0 1023 y

l < (1.5 – 2.0) 10-6 Tomoda (1991), Suhonen (1994)

82Se: T1/2 > 1.0 1023 y

l < 3.2 10-6 Tomoda (1991)

Limit on the effective mass of the Majorana neutrino,

on Majoron and on V+A

Limits on T1/2 are @ 90% C.L.

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

Free-Radon Purification 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 :Tent surrounding the detector

May 2004

August 2004 : Radon-free

SuperKamiokande-like

Air Factory

Expected activity:

A(222Rn) ~ 0.2 Bq/m3

150 m3/h

500 kg charcoal @ -40oC

Expected Purification Factor ~ 75

Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

NEMO-3 Expected sensitivity

(after 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 = 7.7 1018 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) > 4 .1024 y (90% C.L.)

    <mn> < 0.2 – 0.35 eV

    932 g of 82Se T1/2(bb0n) > 8 .1023 y (90% C.L.)

    <mn> < 0.65 – 1.8 eV

    (conservative limit)

    Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


    Nemo 3 experiment n eutrino e ttore m ajorana o bservatory first results

    CONCLUSIONS

    • 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 140 000 2b2n events collected

      100Mo: in favour of Single State Dominance (SSD)

      100Mo bb2n decay to excited state has been measured with ~ 4 s

    • Preliminary T1/2(bb0n) limit (216.4 days of data):

      • 100Mo (4.10 kg.y) T1/2(bb0n) > 3.5 1023 y mn < 0.7 – 1.2 eV

      • 82Se (0.55 kg.y) T1/2(bb0n) > 1.9 1023 y mn < 1.3 – 3.6 eV

    • Level of backgounds as excepted exceptRadon ~ 10 times too high

      Free radon purification system in operation in August 2004

      Supression factor ~ 75

    • Expected sensitivity in 5 years after radon purification

      • 100Mo: T1/2(bb0n) > 4 .1024 y <mn> < 0.2 – 0.35 eV

      • 82Se: T1/2(bb0n) > 8 1023 y <mn> < 0.65 – 1.8 eV

    Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004


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