Post on 28-Jan-2016
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