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

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)

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

June 2002 : tests runs

February 2003 : beginning of data taking

The The NEMO3 detectorNEMO3 detectorThe The NEMO3 detectorNEMO3 detector

AUGUST 2001

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

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

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

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 )

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

Background substractedNEMO 3

22 Monte Carlo

100Mo 22angular distribution

100Mo 22angular distribution

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

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

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

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

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)

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

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

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