Recent Results of the NEMO 3 Experiment

Ladislav VÁLACzech Technical University in Prague

NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy

Outline

Double beta decay

NEMO 3 description

NEMO 3 results(2 & 0 & 0)

Conclusion

IntroductionIntroduction

Double beta decay

Two-neutrino decay (2): (A,Z)→(A,Z+2) + 2 e + 2e

0 & 0: L = 2 process

• Majorana neutrino ≡ and effective mass m

• Light neutrino exchange → m

• Right-handed (V+A) current in weak interaction

→ m,

• Majoron emission → gM

• SUSY particle exchange →

with Majoron emission (0): (A,Z)→(A,Z+2) + 2 e +

Neutrinoless decay (0): (A,Z)→(A,Z+2) + 2 e

Wn

n

p

p

e

e

M

W

eR

eL

h

h

0

Neutrinoless Double Beta Decayar

bit

rary

un

its

(Q ~ MeV)

Two electron energy spectrum

T02/1

Experimental signature:2 electronsE1 +E2 = Q

0 = (T1/2)-1 = G0(Q5,Z) |M0|

2 m2

G0 – phase space factor M – nuclear matrix elementm – effective neutrino mass

m = | j |Uej|2 eij mj |

NEMO 3 description

NEMO 3 description

NEMO 3 Collaboration

CEN Bordeaux-Gradignan, FranceCharles University, Prague, Czech Republic

Czech Technical University, Prague, Czech RepublicINEEL Idaho Falls, USA

INR Moscow, RussiaIReS Strasbourg, France

ITEP Moscow, RussiaJINR Dubna, Russia

Jyväskylä University, FinlandLAL Orsay, France

LSCE Gif-sur-Yvette, FranceLPC Caen, France

University of Manchester, United KingdomMount Holyoke College, USA

Kurchatov Institute, Moscow, RussiaSaga University, Japan

University College London, United Kingdom

B (25 G)

4 m

20 sectors

3 m

6 m

6 m

Detector located in the Fréjus Underground Laboratory, France (4800 m.w.e.)

Source: 10 kg of isotopes, cylindrical, S = 20 m2, foils ~ 60mg/cm2

Tracking detector: drift wire chamber operating in Geiger mode(6180 cells)gas = 94% He + 4% ethyl alcohol + 1% Ar + 0.1% H2O

Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTsMagnetic field: 25 GaussGamma shield: pure iron (18 cm layer)Neutron shield: borated water (ext. wall, 30 cm layer) & wood (top and bottom, 40 cm layer)

NEMO 3 detector

identification of e–, e+, and -particles

116Cd 405 gQ = 2805 keV

96Zr 9.4 gQ = 3350 keV

150Nd 37.0 gQ = 3367 keV

48Ca 7.0 gQ = 4272 keV

130Te 454 gQ = 2529 keV

natTe 491 g

Cu 621 g

2 decaymeasurement

External background measurement

100Mo 6.914 kgQ = 3034 keV 0 decay search82Se 0.932 kg

Q = 2995 keV&

NEMO 3 sources

event from data

Deposited energy: E1 + E2= 2088 keVInternal hypothesis: (t)mes – (t)theo = 0.22 nsCommon vertex: (vertex) = 2.1 mm (vertex)// = 5.7 mm

Run Number: 2040Event Number: 9732Date: 2003-03-20

100Mo foils

Scintillator+ PMT

Longitudinal viewTransverse view

Vertex of the ee emission

Vertex of the ee emission

External background 208Tl (PMTs) Measured with (e) external events~ 10-3 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV

~ 0.1 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV

208Tl impurities inside the foils Measured with (e2), (e3) events coming from the foil

External neutrons and high energy ’s Measured with (ee)int events with E1+E2 > 4 MeV

0.02 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV

NEMO 3 can measure each component of its background!

100Mo 2 decay T1/2 = 7.1 × 1018 y ~ 0.3 0-like events y-1·kg -1 with 2.8<E1+ E2<3.2 MeV

Background measurement

Radon background

~ 1 0-like event/y/kg with 2.8 < E1+E2 < 3.2 MeV

Radon was the dominant background forthe 0 search in the NEMO 3 Phase I data !!!

Radon was the dominant background forthe 0 search in the NEMO 3 Phase I data !!!

Radon in the NEMO 3 gas of the wire chamber

Due to a tiny diffusion of the radon of the laboratoryinside the detector: A(Rn) in the lab ~15 Bq/m3

Two independent measurements of

radon in the NEMO 3 gas

Good agreement between the two measurements

1. Radon detector at the input/output of the NEMO 3 gas

2. (1e + 1) channel in the NEMO 3 data

A(Rn) inside NEMO 3 20-30 mBq/m3 (Phase I)

222Rn (3.8 days)

218Po

214Pb

214Bi

214Po

210Pb

s

Decay inthe gas

delayed

214Bi → 214Po (164 s) → 210Pb

Radon trapping facility

Start-up: October 4th 2004

1 ton of charcoal @ –50oC, 9 barsair flux = 150 m3/h

Input: A(222Rn) 15 Bq/m3

Output: A(222Rn) < 15 mBq/m3 !!!reduction factor of 1000

NEMO 3 tent: factor of 100 – 300

inside NEMO 3: factor of 10A(222Rn) 2 mBq/m3

February 2003 – September 2004: Phase I (radon background in data)Since October 2004: Phase II (radon level reduced by a factor of 10)

Radon backgroundis negligible today!

Radon backgroundis negligible today!

0.015 Bq/m3

Radon trapping facility

chilling unit

charcoal columns

compressorbuffer

dryer

NEMO 3 results

NEMO 3 results

100Mo: 2 decay

T1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ] 1018 y

Phys. Rev. Lett. 95 (2005) 182302

T1/2 = [ 7.11 ± 0.02 (stat) ± 0.54 (syst) ] 1018 y

Phys. Rev. Lett. 95 (2005) 182302

219 000 events6914 g

389 daysS/B = 40

cos(ee)

Data2 MCsimulation

Background subtracted

Sum Energy Spectrum Angular Distribution

Data2 MCsimulation

Background subtracted

219 000 events6914 g

389 daysS/B = 40

E1 + E2 (MeV)

2 HSDMC simul.

Background subtracted

• Data

Esingle (keV)

HSD

2/ndf = 139./36

Esingle (keV)

2 HSDMC simul.

Background subtracted

• DataSSD

2/ndf = 40.7/36

Single electron energy distribution of the 2 decayof 100Mo in favor of Single State Dominance (SSD) model

Single electron energy distribution of the 2 decayof 100Mo in favor of Single State Dominance (SSD) model

Single electron spectrumdifferent between SSD and HSD

Šimkovic et al., J. Phys. G 27 (2001) 2233.

Esingle (keV)

HSD, higher levels contribute to the decay

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

100Mo

0+

100Tc

1+

100Mo: decay to exc. states

2 decay to the 01+ state: S/B = 3.0

T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y

0 decay to the 01+ state:

T1/2 > 8.9 1022 y @ 90 % C.L.

2 decay to the 21+ state:

T1/2 > 1.1 1021 y @ 90 % C.L.

0 decay to the 21+ state:

T1/2 > 1.6 1023 y @ 90 % C.L.

To be published soon, submitted to Nucl. Phys. A

2 decay to the 01+ state: S/B = 3.0

T1/2 =[ 5.7+1.3-0.9(stat) ± 0.8(syst)]1020 y

0 decay to the 01+ state:

T1/2 > 8.9 1022 y @ 90 % C.L.

2 decay to the 21+ state:

T1/2 > 1.1 1021 y @ 90 % C.L.

0 decay to the 21+ state:

T1/2 > 1.6 1023 y @ 90 % C.L.

To be published soon, submitted to Nucl. Phys. A

Clear topology:

01+: 2e- + 2 in time & energy and TOF cuts

21+: 2e- + 1 in time & energy and TOF cuts

100Mo

0+

21+ (540 keV)

01+ (1130 keV)

41+ (1227 keV)

0+ (g.s.)100Ru

22+ (1362 keV)

303

4 k

eV

1

2

334.3 days of data (Phase I)

100Mo: 0 decay

Energy window: 2.78 MeV < Eee < 3.20 MeV

14 events observed, 13.4 events expected

7.9 events excluded at 90% C.L.

V-A: T1/2 > 5.8 × 1023 y @ 90% C.L.

m < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4]

V+A: T1/2 > 3.2 × 1023 y @ 90% C.L.

< 1.6 × 10-6 [5]

Energy window: 2.78 MeV < Eee < 3.20 MeV

14 events observed, 13.4 events expected

7.9 events excluded at 90% C.L.

V-A: T1/2 > 5.8 × 1023 y @ 90% C.L.

m < (0.6 – 0.9) eV [1-3], < (2.1 – 2.7) eV [4]

V+A: T1/2 > 3.2 × 1023 y @ 90% C.L.

< 1.6 × 10-6 [5]

693 days of dataPhase I + Phase II

[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.[5] J.Suhonen et al., Nucl.Phys. A 700 (2002) 649.

NM

E:

T1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ] 1019 y

Phys. Rev. Lett. 95 (2005) 182302

T1/2 = [ 9.6 ± 0.3 (stat) ± 1.0 (syst) ] 1019 y

Phys. Rev. Lett. 95 (2005) 182302

2750 events932 g

389 daysS/B = 4

Sum Energy Spectrum

Data2 MCsimulation

Background subtracted

E1 + E2 (MeV)

82Se: 2 decay

82Se: 0 decay

Energy window: 2.62 MeV < Eee < 3.20 MeV

7 events observed, 6.4 events expected

6.2 events excluded at 90% C.L.

V-A: T1/2 > 2.1 × 1023 y @ 90% C.L.

m < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4]

V+A: T1/2 > 1.2 × 1023 y @ 90% C.L.

< (2.8 – 3.0) × 10-6 [6]

Energy window: 2.62 MeV < Eee < 3.20 MeV

7 events observed, 6.4 events expected

6.2 events excluded at 90% C.L.

V-A: T1/2 > 2.1 × 1023 y @ 90% C.L.

m < (1.2 – 2.5) eV [1-3], < (2.6 – 3.2) eV [4]

V+A: T1/2 > 1.2 × 1023 y @ 90% C.L.

< (2.8 – 3.0) × 10-6 [6]

693 days of dataPhase I + Phase II

[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica et al., Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese et al., Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.[6] M.Aunola et al., Nucl.Phys. A 463 (1998) 207.

NM

E:

Preliminary results:116Cd: T1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ] 1019 y (SSD)

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

Preliminary results:116Cd: T1/2 = [ 2.8 ± 0.1 (stat) ± 0.3 (syst) ] 1019 y (SSD)

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

116Cd, 150Nd, 96Zr: 2 decay

E1+E2 (MeV) E1+E2 (MeV) E1+E2 (MeV)

116Cd 150Nd 96Zr

2simul.

Data

2simul.

Data

2simul.

Data

818 events37 g

365.4 daysS/B = 2.4

2348 evts405 g

365.4 daysS/B = 7.6

127 events 5.3 g

365.4 daysS/B = 0.9

Background subtracted

48Ca: 2 decay

Preliminary result:

48Ca: T1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ] 1019 y

Preliminary result:

48Ca: T1/2 = [ 3.9 ± 0.7 (stat) ± 0.6 (syst) ] 1019 y

40 events 7.0 g

466.7 daysS/B = 15.7

Very smallbackground!

Phase I + Phase II data

Ee > 0.7 MeV&

cos(ee) < 0

E1+E2 (MeV)

48Ca

0 decay

Netrinoless decay with Majoron emission

(A,Z) → (A,Z+2) + 2e + 0

[1] F.Šimkovic et al.,Phys.Rev. C 60 (1999) 055502.[2] S.Stoica and H.V. Klapdor-Kleingrothaus, Nucl.Phys. A 694 (2001) 269.[3] O.Civitarese and J.Suhonen, Nucl.Phys. A 729 (2003) 867.[4] V.A.Rodin et al., Nucl.Phys. A 766 (2006) 107.

NM

E:

100Mo:

T1/2 > 2.7 × 1022 y @ 90% C.L.

gee < (0.5 – 1.9) × 10-4

100Mo:

T1/2 > 2.7 × 1022 y @ 90% C.L.

gee < (0.5 – 1.9) × 10-4

82Se:

T1/2 > 1.5 × 1022 y @ 90% C.L.

gee < (0.7 – 1.7) × 10-4

82Se:

T1/2 > 1.5 × 1022 y @ 90% C.L.

gee < (0.7 – 1.7) × 10-4

Nucl. Phys. A 765 (2006) 483.

334.3 days of data (Phase I)

ConclusionConclusion

New measurement and T1/2 limits for decay of 100Mo to

excited states

Conclusion

No signal seen for 0 decay

Improved limits:

100Mo: T1/2 > 5.8 × 1023 y, m < (0.6 – 2.7) eV

82Se: T1/2 > 2.1 × 1023 y, m < (1.2 – 3.2) eV

Improved limits for 0 decay of 100Mo and 82Se

2 decay of 100Mo and 82Se measured with high statistics

Preliminary results for other isotopes

Analysis of Phase II data in progress

Spare Slides About

SuperNEMO

Spare Slides About

SuperNEMO

SuperNEMOSuperNEMO

Ladislav VÁLACzech Technical University in Prague

NOW2006, 9th – 16th September 2006, Conca Specchiulla, Italy

extension of the NEMO 3 technique 100–200 kg of isotopes, thin source between

tracking volumes, surrounded by calorimeter.

sensitivity T1/2(0) > 1026 y, m < 50 meV

main improvements needed: energy resolution (FWHM @ 3 MeV = 4%) detection efficiency (factor of 2) source radio purity (factor of 10) background rejection methods

SuperNEMO Project

NEMO collaboration + new labs ~ 60 physicists, 11 countries, 27 laboratories

USAMHCINL

(U. Texas)

JapanU. Saga

U. Osaka

FranceCEN Bordeaux

IReS StrasbourgLAL OrsayLPC Caen

LSCE Gif/Yvette

UKUC London

U ManchesterIC London

FinlandU. Jyväskylä

RussiaJINR DubnaINR MoscowITEP Moscow

Kurchatov Institute

UkraineINR Kiev

ISMA Kharkov

Czech RepublicCharles U. Prague

CTU Prague

MaroccoFes U.

SlovakiaU. Bratislava

SpainU. ValenciaU. Zarogoza

U. Autonoma Barcelona

SuperNEMO Collaboration

14 m

3 m

For each module:Calorimeter : 300 to 1000 PMT’s(depending on the final design)Resolution (FWHM) at 3 MeV = 4%

Tracking : drift chamber (3000 cells in Geiger mode)

Magnetic field : 25 gauss

Water shield: 2kT of water for 20 modules

Source foil: 5 kg of enriched 150Nd or 82Se

Number of modules = 20

(0) ~ 30 %

Possible Design

Goal : T1/2 1026 y m 50 meV

The best choice for phase space and background

Q = 3.367 MeV150Nd

Radiopurity requirements for the source

208Tl < 2 Bq/kg

T2 = 9 x1018 y Expected background from 2 = 2.2 evt/500kg.y in 200 keV

Enrichment by laser (200 keV energy window at Q)

Phase space factor G0 = 8.00 x 10-25 y-1eV-2

Sources = G M m2

T1 2

Q = 2.995 MeV Phase space factor G0 = 1.08 x 10-25 y-1eV-282Se

T2 = 9 x 1019 y Expected background from 2 = 1.4 evt/500kg.y in 200 keV

Enrichment by ultracentrifugation

214Bi < 10 Bq/kg208Tl < 2 Bq/kg Rn < 2 Bq/m3

Radiopurity requirements for the source

(200 keV energy window at Q)