FIRST RESULTS OF THE NEMO 3 EXPERIMENT Laurent SIMARD LAL Orsay (France) HEP-EPS 2003 conference...
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FIRST RESULTS OF THE NEMO 3 EXPERIMENT
Laurent SIMARDLAL Orsay (France)
HEP-EPS 2003 conference
CENBG, IN2P3-CNRS et Université de Bordeaux, FranceCFR, CNRS Gif sur Yvette, FranceFNSPE, Prague University, Czech RepublicINEEL, Idaho Falls, USAIReS, IN2P3-CNRS et Université de Strasbourg, FranceINR RAS, Moscow, RussiaITEP, Moscow, RussiaJINR, Dubna, Russia Jyvaskyla University, FinlandLAL, IN2P3-CNRS et Université Paris-Sud, FranceLPC, IN2P3-CNRS et Université de Caen, FranceMount Holyoke College, USARRC “Kurchatov Institute”, Moscow, RussiaSaga University, JapanUniversity College London, United Kingdom
NEMO collaboration
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L = 2 Process Majorana Neutrino and
effective mass <m>
Right-handed current in weak
interaction
SUSY particle exchange
Majoron emission
(0) : 2n 2p+2e-
W
Wn
n
p
p
e
e
M
eR
eL
( )T0
2/1
h
h
DDouble bêta ouble bêta (0(0) ) decaydecay : Physics : Physics beyond the standard modelbeyond the standard model
DDouble bêta ouble bêta (0(0) ) decaydecay : Physics : Physics beyond the standard modelbeyond the standard model
(Q ~ MeV)
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B25G
3 m
located in the Laboratoire Souterrain de Modane (4800 mwe)
10 kg of isotopes(surface: 20 m2, thickness: 60 m for 100Mo)
6180 drift cells operating in Geiger mode: (Helium+ethyl alcohol (4 %) + argon (1 %))
Calorimeter : 1940 plastic scintillators coupled to low radioactivity PMs(E)/E at 3 MeV = 3.5 %
Magnetic field (25 Gauss) + Iron shielding (18 cm) + neutron shielding (35 cm water +wood)
Source :
Tracking :
Shielding :
Calorimeter :
The NEMO3 The NEMO3 detectordetector
The NEMO3 The NEMO3 detectordetector
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June 2002 : tests runs
February 2003 : beginning of data taking
The The NEMO3 detectorNEMO3 detectorThe The NEMO3 detectorNEMO3 detector
AUGUST 2001
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7.2 kg 100Mo1 kg 82Se
0.4 kg 116Cd0.6 kg 130Te1 kg natTe0.6 kg Cu
background
48 g 150Nd20 g 96Zr7 g 48Ca
The sources in The sources in NEMO3NEMO3
The sources in The sources in NEMO3NEMO3
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Identification of the particles : e,,
Calorimeter
Magnetic field Distinction between e- and e+
Tracking Distinction between e and Delayed track ( until 700 s
Potentialities of the NEMO3 Potentialities of the NEMO3 detectordetector
Potentialities of the NEMO3 Potentialities of the NEMO3 detectordetector
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Canal 1 e-: 1 MeV) =cm; 0.5 MeV) =cm 1 MeV) =cm; 0.5 MeV) =cm
Reconstruction of vertex (runs with 207Bi sources)
Performances of the NEMO3 Performances of the NEMO3 detectordetector
Performances of the NEMO3 Performances of the NEMO3 detectordetector
Energy calibration(with 207Bi and 90Sr sources)
207Bi
482 keV
976 keV
207Bi : 0.5 MeV and 1 MeV
90Sr : 2.3 MeV
1 MeV) =
ADC channel
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Selection of electron-electron events
Selection of electron-electron events
1256 keV
832 keV
• 2 e- tracks associated with PMs hits, originated from the same vertex on the foil •Time of flight : decay in the source •No delayed hit near the vertex (rejection of )
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6 5 0 h o u r s1 3 7 5 0 e v e n t s
S / B = 4 0
B a c k g r o u n d s u b s t r a c t e d
T1 / 2 = 7 . 8 0 . 0 9 ( s t a t ) 0 . 8 ( s y s t ) 1 0 1 8 y
2 2 M o n t e C a r l oN E M O 3
S/B~100 si E1+E2 > 1000 keV
100Mo 22 preliminary results
100Mo 22 preliminary results
Feb-Mar 2003
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Background substractedNEMO 3
22 Monte Carlo
100Mo 22angular distribution
100Mo 22angular distribution
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1850 hours400 events
S/B = 4
Background substracted
Contaminated with -emitters
Cuts: E > 300 keV, Cos () < 0.7
y.100.9(syst.)0.4(stat.)9.1T 191/2
NEMO 322 Monte Carlo
82Se 22preliminary result
82Se 22preliminary result
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Measurement of the background processes, in other channels :
214Bi Channel e (with T1/2 () ~ 164 s
(214Bi -214Po -210Pb)
208Tl Channels e ’s with E= 2.6 MeV
neutrons, and external gammas
e- crossing > 4 MeV
Background at high energyBackground at high energy
2 isotopes which have the greater Q values :• 214Bi : Q3.27 MeV• 208Tl : QMeV
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Study of the background : 208TlStudy of the background : 208Tl
A(208Tl in 100Mo foils) < 100 Bq/kg
look for e, e2, e3 events coming from the foil
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Study of the background : 214BiStudy of the background : 214Bi
~1 0-likeevent due to radon expected in a year (same order of magnitude as the sum of other backgrounds)
anti-radon tent in fall 2003air radon free factory in summer 2004
« anti-radon » tent
Specification : A(214Bi in 100Mo) < 300 Bq/kg
main effect : 222Rn (parent of 214Bi) found in the gas volume
for the moment no limit
given on A(214Bi in 100Mo)
2 measurements of 222Rn activity
by NEMO 3 itself (events e(n))
by radon monitor for the chamber out gasA(222Rn inside NEMO3) ~ 30 mBq/m3
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Efficiency (in[2.8-3.2] MeV 14 %
Internal Background: 208Tl < 0.3 events/year 214Bi < 0.3 events /year
0.8 events /year
External Background: 0. events /year
For 7 kg of 100Mo(Q= 3.038 MeV)
< ~1.4 background events expected in one year
after 5 years data taking
T1/2 >8. 1024 y m < 0.1 - 0.4 eV
For 1 kg of 82Se (Q= 2.995 MeV)
Rejection of « hots spots »
< 0.03 background events expected in one year
after 5 years data taking
T1/2 > 1.5 1024 y m < 0.6 - 1.2 eV
Sensitivity of the NEMO3 detector (limits at the 90% CL
level)
Sensitivity of the NEMO3 detector (limits at the 90% CL
level)
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NEMO 3 is running
Physics runs in LSM since February 14th 2003(~1700 h of data collected until end of May 2003)
T7.8 1018 y (stat error ~1 %)1/2
TSe9.1 1019 y (stat error ~4 %)1/2
ConclusionConclusion
Study of detector performance with tests runs(june to december 2002)
tracking and calorimeter performance in agreement with design
Results for 0 in 2004
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N
SEW
Fall 2003 : A(222Rn) ~5 Bq/m3
Now : A(222Rn) in the LSM ~10 Bq/m3
Mid 2004 : A(222Rn) ~0.2 Bq/m3
Anti-radon tent for NEMO3 detector
Anti-radon tent for NEMO3 detector
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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 HSD ans SSD mechanismMo 22 HSD ans SSD mechanism