First results from NEMO 3 　 Experiment

V. Vasiliev (ITEP), H. Ohsumi (Saga) and Ch. Marquet (CENBG)

@NDM03, Nara, Japan, June 2003

NEMONEMO collaboration collaboration

CENBG, IN2P3-CNRS and University of Bordeaux, France

CFR, CNRS Gif sur Yvette, France

Czech Technical University, Prague, Czech Republic

INEEL, Idaho Falls, USA

IReS, IN2P3-CNRS and University of Strasbourg, France

ITEP, Moscow, Russia

JINR, Dubna, Russia

Jyvaskyla University, Finland

LAL, IN2P3-CNRS and University of Paris-Sud, France

LPC, IN2P3-CNRS and University of Caen, France

Mount Holyoke College, USA

Saga University, Japan

University College London, UK

NEMONEMO 3 collaboration 3 collaboration

1. Introduction (about our final goal) 1. Introduction (about our final goal)

2. Detector Performances, Present status, Backgrounds2. Detector Performances, Present status, Backgrounds

3. An example of background results (Cu foils) 3. An example of background results (Cu foils)

4. Present status of the data analysis 4. Present status of the data analysis

5. Preliminary results of the first stage5. Preliminary results of the first stage

6. Conclusions6. Conclusions

(I) H. Ohsumi (and Ch. Marquet)

(II) V. Vassiliev

Neutrinoless Double Beta Decays ( Majorana ? <mν> ? or new physics ?

Measure several isotopes ( 100Mo , 82Se , 130Te , 116Cd, 96Zr , 48Ca , 150Nd

Tag and measure all the BG events e-, e+, , , neutron Tracking chamber+Calorimeter+B-field+Shields

““zero background” experimentzero background” experiment

Just to remind you the Just to remind you the original idea original idea of NEMOof NEMO

E(1+2) Q

→

The NEMO3 detectorThe NEMO3 detector Fréjus Undergroud Laboratory : 4800 m.w.e.

Identification : eIdentification : e--, e, e++, , , n and delayed-, n and delayed- events detection Measurement of source radiopurity Background measurement and rejection

3 m

4 m

(25 G)

B

Source : isotopes (7kg 100Mo, 1kg 82Se…..) cylindrical, S = 20 m2, e = 60 m

Tracking detector : He+ alcohol(5%) +Ar(1%)

drift wire chamber operating in Geiger mode (6180 cells)

Calorimeter : 1940 plastic scintillators coupled to low radioactivity PMs (E)/E at 3 MeV ~ 3.5%

Magnetic field: 25 Gauss

Iron shielding: e = 20 cm

Neutron shielding: water +wood+parafin

20 sectors

1 sector of NEMO3

Tracking detector (6180 Geiger cells in He+alcohol(5%)+Ar(1%)): Vertex t = 4 mm, z = 0.8cm Calorimeter (1940 plastic scintillators – PMTs low radioactivity) FWHM~14% (e @1 MeV) Iron shield (20cm) + water shield + wood shield + parafin magnetic field B=25 G materials low radioactivity Frejus Underground Laboratory (LSM) 4800m.w.e.

NEMO3 : Neutrino Ettore Majorana ObservatoryNEMO3 : Neutrino Ettore Majorana Observatory

October

2001

July

2002

Sources preparationSources preparation

T0

2/1 > 8. 1024 y

<m> < 0,1 – 0,3 eV

NBkg=0,2 evts y-1 kg-1

(90% C.L.)

NBkg=0,02 evts y-1 kg-1

T0

2/1 > 1,5 1024 y

<m> < 0,45 – 1,2 eV(90% C.L.)

Bkg

Sources thicknessmg/cm2)

Q= 3034 keV Q= 2995 keV

82Se (0.93 kg)100Mo (6.9 kg)

Sources in NEMO-3 detectorSources in NEMO-3 detector

Expected Sensitivityafter 5 years :

) <0,04(214Bi) <0,04(208Tl) ),....

Requirements:

<0.02mBq/kg(208Tl)

<0.3mBq/kg(214Bi)

Composant Poids

approx. (kg)

Total Activity (in Bq)

PMs

600

830

300

18

Cuivre

25000

< 625

< 42

< 20

< 13

Fer

10000

< 50

< 6

< 8

17 4

Scintil.

5000

< 58

< 6

< 2

métal

2000

< 70

< 7

4 1

3 1

Fils

1.7

< 8. 10-2

< 2. 10-3

< 2. 10-5

10-2

Air

40

300

Component Weight

(kg)

PetalsIron

Wires

Copper

40K 214Bi 208Tl 60Co

Notmeasured

<125 < 25 < 10 < 6

<100 <0.7 <0.3 1.8.4

<17 < 2 2.0.7 4.3.7

<8 10-3 < 10-3 <6 10-4 10-2

~20 Shielding

Iron180000

<3000 <300 <300 300 100

~300

600 830 300 18

5000

Total Activities

NEMO 3

By ultra low level

g-ray spectroscopy

with Ge

NEMO (200tons)

~300Bq (214Bi)

Human body (60kg)

~5000Bq (40K)

t ~ 0 ns

t 3 ns

t ~0 ns

t ~ 0 ns

--

e-

e-

e+ or e-

-

e-

« Crossing e- »

e+e pairs-

Double ComptonCompton + Möller

-

-

t ~0 ns

Signal

Internal background

External background

Source contaminations

n

source foil

How detect signals and tag the background ?

　　　

Tracking (Identification e/others)

Delayed (<700s) track

Calorimeter ()~50% (@0.5MeV)

Possible for tagging e, e, e, …

Time of flight t~300ps(@1MeV)

External Background rejection

Magnetic Field (Identification e-/e+)

3~5% e-/e+ confusion @ 1~7MeV

214Bi Tagged by e() (~164s)

( 214Bi->214Po->210Pb)

208Tl e, e, e, with (2.6MeV)

or Taggd by e() (~300ns)

( 212Bi->212Po->208Pb)

Neutron Crossing e (4~8MeV)

Study of Background Process

Identification of e, , B=25G

(2) decay

(0) decay

Brief summary of NEMO Performances

NEMO-3 STATUS

• Jan. 2001: first events with 3 first sectors mounted with no magnetic field and no shield

• Sep. 2001: full detector mounted and assembled• Dec. 2001: first events with the full detector

with no magnetic field and no shield• Feb. 2002: Coil (magnetic field) mounted• Mar. 2002: first events with the full detector

with magnetic field (no shield)• Apr. 2002: Iron shield mounted • Jun. 2002 Dec. 2002: Test runs with iron shield + magnetic field ~1500h (1200h) (Period I)• Dec. 2002 Feb. 2003: Shutdown for the last tuning (to improve reliability)• 14 February 2003 : START TAKING DATA ~2000h (650h) (Period II) (We will mainly report the data of this period)And also: • Runs with calibration sources (Sr90, Bi207, Co60) for energy and time calibration• Runs with neutron source for tracking vertex resolution: for testing neutron shielding (water + wood)• Runs for testing iron shield run with and without iron shield • Radon studies

Z v

erte

x (c

m)

Rvertex (cm) 1 sector of NEMO3

A vertical flat calibration tube

207Bi (~220Bq) x 3 x 20 482keV, 976keV (ICE)

Run with calibration sources ( 207Bi example)

Distribution of reconstructed vertices

Z

Geometry of the tracking detector

Determination　of　the　vertex4 rows

Tracking curvature2 rows

3 rows Determination of the impact on the scintillator

Resolution on the 2e- channel

R) = 0.6 cm z) = 1.8 cm

⊥= 0.4 cm // = 0.8 cm

8 cathodic wires (0 V)1 anodic wire (HT 1900 V)

vertical drift cells operating on Geiger mode

using 2 conversion electrons of 207Bi

Energy Calibration

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

207Bi

482 keV

976 keV

90Sr

End point 2,28 MeV

207Bi+90Sr

E(keV)=A*ch+B

A=3.350±0.034keV/ch

B=23.5±9.17 keV

Daily survey with a LASER

7 references : 6 PMs coupled to a 207Bi source + average on all the NEMO3 PMs

laser e- 207Bi

900PM 5”

1040PM 3”

Photodiode

(Intensity Monitor)

Optical Filters (known transmissions)

Daily check of E (Gain) and t

PMT E linearity (0 ~ 12MeV)

Determination of t-E relation

Gain survey for 3 PMs during 2 months (obtained with the laser system)

PM : 2.1.1.4

PM : 18.1.1.0 PM : 19.3.1.0

Typical PM

few PMs with pathological behaviourVariation then stabilisation

Time Of Flight RejectionTime Of Flight Rejection

External Background(Crossing electron)

events from the foil

(tmes – tcalc) external hypo. (ns)

(tmes – t

calc ) internal hypo. (ns)

An example of

2 track events on 100Mo Foils

Time Alignment

(Studied by 60Co Source)

t ~ 300ps

@1MeV

2 event

EVENT OBSERVED BY NEMO-3… EVENT OBSERVED BY NEMO-3…

1256 keV

832 keV

E1+E2= 2088 keV

(t)mes –(t)theo = 0.22 ns(vertex) = 2.1 mm(vertex)// = 5.7 mm

Electron + N ’s 208Tl (E = 2.6 MeV)

Electron crossing > 4 MeV Neutron capture

BACKGROUND EVENTS OBSERVED BY NEMO-3… BACKGROUND EVENTS OBSERVED BY NEMO-3…

Electron + delay track (164 s) 214Bi 214Po 210Pb

Electron – positron pair B rejection

208Tl Radioimpurity of the 100Mo (7kg) sources

Study of the e- e- e- channels of 208Tl decay

Preliminary, to be improved with more data(NEMO requirement: 20 Bq/kg)

Most « dangerous » background for study

Conservative value (90%CL)

A(208Tl) < 50 Bq/kg 208Tl

channel e e e100Mo(data) 1 4 0

100Mo(MC) 1.5 1.7 0.3

(MC calculation for 20Bq/kg of 208Tl)

(890 hours of data)

e(n = 5 event

214Bi effect from Radon

1. Rn level Air in room ~10Bq/m3 (Normal) Inside of NEMO ~30mBq/m3 (Very Low)2. Process (in He+Alcohol gas) where is 214Bi ? wire ? gas? or foils ?3. Contributions 2 not dangerous 0 less than 2 events/year

( We are in the border line of our requirement)

4. Radon free air facility This fall reduce factor 2 Next year reduce ~50

214Bi study by NEMO itself

Radon monitor for chamber out gas

NEMO requirement :to the source 0.3 mBq/kg

Electron + delay track (164 s) 214Bi 214Po 210Pb

Sensitivity

~1 mBq/m3

70 litter

222Rn

218Po+(?) 214Bi+

-1500V

Comparison neutron simulation with Data from a AmBe source (neutrons: <En> 5MeV + : E=4,43 MeV)

With Iron shield + B=25 G : 4,43 MeV stopped by iron shield

(e crossing + n)

DATA

Monte Carlo neutrons

H

Fe+Cu

Fe

Fast neutrons simulation with 20 cm of iron shield Expected number of events above 2,75 MeV after 5 years

With neutron shield 0 event above 2.75 MeV (After 5 years):with a rejection factor of ~ 70

E>2,75 MeV E[2,75-3,2] MeV

(e-e-)

t=0ns

(13,64,4) (1,1+2,2 )-0,8

Neutron Background

n fast

e-

n thermalized

Copper frame

plastic scintillator

AmBe source(out of shield)

Without n shield

Sensitivity of NEMO3 to measure sources of backgroundSensitivity of NEMO3 to measure sources of background

Design NEMO3 for 10 kg: 208 Tl in source foils < 0.02 mBq/kg 214 Bi in source foils < 0.3 mBq/kg neutron flux < 10-8 n cm-2 s-1

Sensitivity NEMO3 after 1 year of data :

208 Tl in source foils < 2 Bq/kg channel e ’s (E= 2.6 MeV) 212 Bi 212 Po e (300 ns) 214 Bi in source foils < 2 Bq/kg

measured by channel e (  ( 214 Bi 214 Po 210 Pb; T1/2 = 164 s )

neutrons < 10-9 n cm-2 s-1

measured by e- crossing > 4 MeV

Sensitivity to 100 kg of isotopes

a factor 10 better!

a factor 100 better!

a factor 10 better!

See A. Barabash talk: NEMO extrapolation

An Example of Background Results

Cu Foils (0.62kg) （ (I)1200h+(II)650h=1850h 78 days)

Using the same analysis of decay

(Just for an introduction to the next analysis part)

53 events (78days) 0.7 event/day

No event above 2.6MeV

Cu E1+E2

3MeV

Data analisys in NEMO. Data analisys in NEMO.

　22　decay　analysis.• Estimation of background.

• External rays.• Rn in the tracking chamber• Radioactive impurities in source foils

• Selection of electron-electron (2e) events.• Efficiency estimation. Half-life value.• Consistence of experimental energy and angular distributions with MC.

　20　decay　analysis.• Search for candidate 20 events.• Estimate efficiency.• Estimate background.• Conclusion about half-life and neutrino mass.

Background, external . Background, external .

　electron+　events

keV200

keV300

E

E

Time of flight incoming

Good agreement

TlBiK

CarloMonte20821440

Background, Rn in the gas. Background, Rn in the gas.

　electron+　events

0.45- )( Cos

keV]1800,1100[

keV350

E

E

TOF decay near the source

　electron+　delayed　　　　　　:cutstheindecayBidetect 214 :decay s)(164μPoBidetect 214214

3Rn mBq/m1.832A

3Rn mBq/m5.030A

Background, pollution in source. Background, pollution in source.

　single　electron　eventskeV1000E

TlPb

Pa

:emittersβpureMeasure

207211

234m

　Ge　detector　

Ac

K

: cascade ity with radioactivMeasure

228

40

Good agreement

keV

Single electron energy

TlPbPa

CarloMonte207211234m

Selection of electron-electron events.Selection of electron-electron events.

• 2 tracks reconstructed + 2 associated PMTs• each particle has negative charge• electron energy > 200 keV• Time of Flight decay inside the source • common vertex• vertex in source material• nearest to the source geiger layer is hit• no delayed geiger hits near the vertex

Mo 22 preliminary results.Mo 22 preliminary results.

650 hours13750 events

S/B = 40

Background substracted

T1/2= 7.8 0.09 (stat) 0.8 (syst) 1018 y

22 Monte CarloNEMO 3

Mo 22, angular distribution.Mo 22, angular distribution.

Background substractedNEMO 322 Monte Carlo

Mo 22, HSD and SSD mechanism.Mo 22, HSD and SSD mechanism.

HSD, higher levels contribute to the decay

SSD, 1+ level dominates in the decayAbad et al., 1984, Ann. Fis. A 80, 9

Calculations for Mo:F. Simkovic et al., J. Phys. G, 27 (2001) 2233-2240

Effect in one electron spectrum

NEMO • High 22 statistics• Measures each electron could see it!

100Mo

0+

100Tc

100Ru

1+

0+

Mo 22 electrons energy. Mo 22 electrons energy. Background substracted

Different predictions for T1/2:

T1/2(HSD)= 7.8 0.09 (stat) 0.8 (syst) 1018 y

T1/2(SSD)= 7.0 0.09 (stat) 0.8 (syst) 1018 y

NEMO 3 NEMO 3

Mo 20 preliminary result. Mo 20 preliminary result.

• 20 energy region [2.75,3.2] MeV• 1 event 20 candidate, 650 h. of data analysed, no laser corrections.• = 10 %• Conservative limit

eV2.71.2m

C.L.)(90%y.106T

ν

2201/2

　20　decay

• energy region [2.6,3.2] MeV• 9 candidate event (650 h.), 5 expected.• = 0.7 %• Conservative limit

4ee

2101/2

10)70.156.0(g

C.L.)(90%y.108.1T

　20　decay

Se 22 preliminary result. Se 22 preliminary result.

1850 hours400 events

S/B = 4

Background substracted

Contaminated with -emitters

Cuts: E > 300 keV, Cos () < 0.7

C.L.)(90%102.5)(0.9gy.,108T

C.L.)(90%eV7.032.55my.,104.7T4

ee210ν

1/2

ν220ν

1/2

y.100.9(syst.)0.4(stat.)9.1T 191/2

NEMO 322 Monte Carlo

1850 hours336 events

S/B = 3.4

Background substracted

Cd 22 preliminary result. Cd 22 preliminary result.

y.100.3(syst.))0.15(stat.3.1T 191/2

C.L.)(90%y.107.1T

C.L.)(90%y.10.61T210ν

1/2

220ν1/2

22 Monte CarloNEMO 3

1850 hours147 events

S/B = 3.1

Background substracted

Nd 22 preliminary result. Nd 22 preliminary result.

y.100.8(syst.)0.7(stat.).77T 181/2

C.L.)(90%y.106.2T

C.L.)(90%y.10.41T200ν

1/2

210ν1/2

22 Monte CarloNEMO 3

Conclusion.Conclusion.

• NEMO 3 is taking data with stable conditions. • Tracking chamber and calorimeter pe ｒ forme as expected.• First portion of data analysed and preliminary results for 22 decay of Mo, Se, Cd and Nd were obtained.• Results for 22 decay of other isotopes (Ca, Zr, Te) are expectedend of the year, and for Mo decay on the excited states will be available soon.• Search for neutrinoless and majorana 2 decay is in progress.

Summary.Summary.

Isotope t, hour Nev

T1/2

2, 10

19 y. T

1/2

0,

90% CL.,1022y.

T1/2

0,

90% CL.,1021y.

100Mo 650 137500.78

0.009(stat) 0.08 (syst)

>6.0 >1.8

82Se 1850 4009.1

0.4(stat) 0.9(syst)

>4.7 >8

116Cd 1850 3363.1

0.15(stat) 0.3 (syst)

>1.6 >1.7

150Nd 1850 1470.77

0.07(stat) 0.08(syst)

>0.14 >0.26