Double beta search : experimental view

Laurent SIMARD, LAL - Orsay

6th Rencontres du Vietnam, Hanoi, 6th-12nd August 2006

(0) : 2n 2p+2e-

L = 2 Process Majorana Neutrino and effective mass

<m>

Right-handed current in weak interaction

Majoron emission

SUSY particle exchangeWn

n

p

p

e

e

M

(Q ~ MeV)

( )T0

2/1

W

eR

eL

h

h

Double beta Double beta (0(0) decay:) decay:

Physics beyond the standard modelPhysics beyond the standard model

A=<m> xPSx IM I2 2

Nuc.

Both techniques are complementaryand at least 2 or 3 experiments are needed

to really prove the 0 decay at a level of 5

Modest energy resolution and efficiency Large detector a few 10 m

No signature of the 2 electrons Only 1 observable: total energy

Very high energy resolutionGood efficiency« Compact » detectors (size 10 m)Crystals very pure (surface contamination ?)

Direct signature of the 2 electrons3 observables: - total deposited energy

- individual energy - angular corelation

Possibility to measure various isotopes

Experimental approachesExperimental approaches

Calorimeter

HPGe, Cd – Te bolometers

Tracking + calorimeter

NEMO,EXO

PURE CALORIMETER

The GERDA project (LNGS)

- operate with “naked” Ge diodes in a very pure liquid nitrogen shielding (LN2)- possible upgrade with liquid argon(LAr) for active anticoincidence from the scintillation light of LAr- segmentation of diodes for a greater reduction of backgrounds

The MAJORANA Project in the US210 HPGe segmented diodes in a standard shielding

(500 kg of enriched 76Ge)

Phase III ~ 100 kgSegmented crystalsLiquid Argon 10 years of data-taking

Phase III

10-1 /(keV·kg·y) 10-2 /(keV·kg·y) 10-3 /(keV·kg·y)

Phase I ~ 15 kg 76Ge (crystalsHeidelberg-Moscow + IGEX)

Phase I

(2008)

Phase II ~ 35 kg 76GeSegmented crystals3 years of data-taking

Phase II

(2010)

start with 60 kg

New detectors for Phase II:Procurement of enriched Ge

March ’05: procurement of 15 kg of natural Ge (‘test run’)

Sep ’05: enrichment of 37.5 kg of Ge-76 completed ! ~ 88% Ge-76

April ’06: enriched material transported to Germany; now stored underground at HADES

Specially designed protective steel container reduces activation by cosmic rays by factor 20

Backgrounds in GERDA

Source B [10-3 cts/(keV kg y)]

Ext. from 208Tl (232Th) <1

Ext. neutrons <0.05

Ext. muons (veto) <0.2

Int. 68Ge (t1/2= 270 d) 12

Int. 60Co (t1/2= 5.27 y) 2.5

222Rn in LN/LAr <0.2

208Tl, 238U in holder <1

Surface contam. <0.6

180 days exposure after enrichment + 180 days underground storage

30 days exposure after crystal growing

Target for phase II: B 10-3 cts/(keV kg y) additional bgd. reduction techniques

derived from measurements and MC simulations

Muon veto

Background reduction techniques

• Muon veto

• Anti-coincidence between detectors

• Segmentation of readout electrodes (Phase II)

• Pulse shape analysis (Phase I+II)

• Coincidence in decay chain (Ge-68)

• Scintillation light detection (LArGe)

130Te

Goal: () of 130Te

~ 1000 TeO2 bolometers

Q ~ 2.5 MeV

Experimental data and simulations suggest one major contribute for CUORE background in the DBD region:

and degraded particles emitted by 238U and 232Th surface contaminations on the Cu frame and

on the crystal surface.

BKG = 0.18 ± 0.01 c/(keV kg y)

T1/2 > 2×1024 y @ 90% C.L.

Cuoricino

130Te

TeO2

Cu

TeO2

CUORE : 130Te in LNGS (760 kg of Te)

If background = 0.01 cps/ (keV.kg.year) T1/2() 2.1 x 1026 years (90% C.L.)

If background = 0.001 cps/ (keV.kg.year) T1/2() 6.6 x 1026 years (90% C.L.)

If background = 0.001 cps/ (keV.kg.year) + enriched crystals T1/2() 1.9 x 1027 years (90% C.L.)

After 5 years of data takingFWHM = 5 keV @ 2528 keV

Predictions on the future background expected for CUORE from Cuoricino background analysis and Monte Carlo simulations...

Surface Sensitive BolometersSurface Sensitive Bolometers

Background reduction may be achieved through both passive

and active methods

Creation of a new kind of detectors able to recognize surface events

Identification of background events

Surface

Sensitive

Bolometers

Auxiliary bolometer Main bolometer

SSB

Classic pulse

Classic pulse

Classic pulse

High and fast pulse

Dynamic behavior:

Event originating inside the main bolometer (DBD event)

Event originating outside the main bolometer (degraded )

The difference between heat capacities generates a difference

in pulse height and shape...

Idea: cover each face of a classic bolometer by gluing an active layer, in order to provide a 4 shielding

First SSB experimental results (Como)First SSB experimental results (Como)

Amplitude comparison

According to the described dynamic behavior, various pulse parameters proved to be effective in discriminating surface events.

(Scatter plot)

-Individual thermistor read-out-Parallel thermistors read-out

r on auxiliary thermistor

Bulk events

Surface events

Pul

se a

mp

litu

de

on

aux

ilia

ry N

TD

[m

V]

Pulse amplitude on main NTD [mV]

d on main thermistor

Surface events

Bulk events

Pulse amplitude on main NTD [mV]

Pul

se a

mp

litu

de

on

aux

ilia

ry N

TD

[m

V]

(To be investigated)

14. OUTGASSING

15. REACTIVE CLEANING: Anodic Oxidation and subsequent removal of the oxide16. OZONE CLEANING17. HYDROGEN CLEANING

1. ABRASIVE CLEANING, GRINDING and MECHANICAL POLISHING

2. SOLVENT CLEANING: Chlorofluorocarbons and Liquid CO2 3. SEMI-AQUEOUS CLEANERS: Terpenes; Alcohols; Ketones; Esters; Amines4. ULTRASONIC CLEANING5. MEGASONIC CLEANING6. SAPONIFIERS, SOAPS, AND DETERGENTS7. WIPE-CLEAN8. SUPERCRITICAL FLUIDS

9. CHEMICAL ETCHING10. ELECTROCHEMICAL POLISHING11. ELECTROLESS ELECTROLYTIC CLEANING12. DEBURRING: laser vaporization, thermal pulse flash deburring13. STRIPPABLE COATINGS

18. REACTIVE PLASMA CLEANING AND ETCHING19. PLASMA CLEANING20. SPUTTER CLEANING21. ION BEAM CLEANING

THE POLISHING SYSTEM

The CANDLE project

Prototype CANDLE III is in constructionOsaka-JAPAN

•Pure CaF2 crystals 103 cm3 (scintillation)

• Energy resolution: ~ 5% @ 4.2 MeV

• CANDLES III: 60 crystals : Total mass = 191 kg Crystals natural Calcium

~ 300 g of 48Ca

Technique could be very promising with enriched 48Ca crystals Need to enrich ~ 100-200 kg of 48Ca !...

TRACKING + CALORIMETER

THE EXO PROJECTTPC with Xenon : possibility to use a large mass of isotope

Xe noble gaz : centrifugation -> 200 kg of 130Xe avalaible in Stanford T½ very high

Identification of Ba ion : 136Xe 136Ba++ +2e-

by laser fluoresence

Difficulty: neutralisation Ba++ Ba+

collection of ions

Phase 1: EXO-200, 200 kg of 136XeTPC with liquid Xe, detection of scintillation (FWHM ~ 2% @ 2.5 MeV)No identification of the Ba+ ion Start foreseen end 2007Expected background : 0.003 cts.keV-1.kg-1.y-1

T½ > 3 1025 y

With identification of the Ba+ ion and 1 ton of 136XeExpected background < 0.0005 cts.keV-1.kg-1.y-1

Date ? T½ > 1027 years

3 m

4 m

B (25 G)

20 secteursSource: 10 kg of isotopes cylindrical shape, S = 20 m2, e ~ 60 mg/cm2

Tracking detector: wire chamber in Geiger regime (6180 cells)Gas: He + 4% ethylic alcohol + 1% Ar + 0.1% H2O

Calorimeter: 1940 plastic scintillators coupled to low-radioactivity PMTs

Magnetic field : 25 GaussGamma shielding : Iron (e = 18 cm)Neutron shielding : 30 cm water (ext. wall)

40 cm wood (top and bottom) (since march 2004: borated water)

Able to identify e, e, et

The NEMO3 detectorFrejus Underground Laboratory (LSM) : 4800 m equivalent

water

82Se

Preliminary results of NEMO-3Phase I (with radon) February 2003 - September 2004 : 298 days of data taking

Phase II (without radon) December 2004 - March 2006 : 290 days of data taking 100Mo, 7 kg 82Se, 1 kg

T1/2() > 5.8 1023 (90 % C.L.) T1/2() > 2.1 1023 (90 % C.L.)

T1/2() > 2 1024 (90 % C.L.) T1/2() > 8 1023 (90 % C.L.)Expected in 2009

Phases 1+2

NEMO-3 SuperNEMO

T1/2() > ln2 M Tobs

Nexcluded

Navo

A

7 kg 100 kg Isotope mass M

Efficiency () = 8 % () = 25 %

~ 2 evts / 7 kg / y ~ 1 evt / 100 kg/ y

BackgroundInternal contaminations

208Tl and 214Bi in the foil

214Bi < 300 Bq/kg208Tl < Bq/kg

214Bi < 10 Bq/kg208Tl < Bq/kg

(208Tl, 214Bi) ~ 1 evt/ 100 kg /y(208Tl, 214Bi) ~ 1 evt/ 7 kg /y

T1/2() > 2. 1024 y<m> < 0.3 – 1.3 eV

T1/2() > 1026 y<m> < 0.05 – 0.1 eV

SENSITIVITY

FWHM(calo)=8% @3MeV FWHM(calo)=4% @3MeVEnergy resolution

From NEMO-3 to SuperNEMO

Shielding :Water aganist and neutron Source foil

5,7 m

13 m

4 m

New cavity ~ 70m x 15m x15m

~ 2 000 tons of water for 20 modules

View of the detector in its shielding

• 2009-2010: construction of the 1st module

• 2010: commissioning of the 1st module measurement of the background level• 2010 – 201N: construction of the other

modules• 201N: full detector

Which isotope for SuperNEMO ?

• High phase space factor

• Favorable nuclear matrix element… but uncertain calculations…

• High Q for the background rejection

• Possibility of enrichment !...

Choice criteria for the isotope:

Phase space factorNuclear matrix element

Uncertainties from the theoretical calculations

Effective mass of the Majorana neutrino

= G M ‹m›22

T1/2

1

Half-life of the decay

Which isotope for SuperNEMO ?

Isotope Q (MeV) G (an-1) Shell Model

QRPA

48Ca 4.271 2.44 9.2 1026 2.9 1027

76Ge 2.040 0.24 7 1027 2.4 1027

82Se 2.995 1.08 9.6 1026 7.4 1026

96Zr 3.350 2.24 1.5 1028

100Mo 3.034 1.75 1.4 1027

116Cd 2.802 1.89 1027

130Te 2.528 1.70 3.6 1026 1027

136Xe 2.479 1.81 5.2 1026 2-5 1027

150Nd 3.367 8.00 1.2 1026

T1/2() with m=50meV

With QRPA nuclear matrix elements calculations,100 kg of 150Nd is equivalent to: ~ 340 kg of 82Se ~ 720 kg of 130Te ~ 1010 kg of 76Ge ~ 2640 kg of 136XeBut value of MM00 22 ? ?Shell Model: Caurier et al.

QRPA: Faesller Rodin Simkovic Vogel 2005

Only phase space factor(M=1)100 kg of 150Nd is equivalent to: ~ 410 kg of 82Se ~ 410 kg of 130Te ~ 1700 kg of 76Ge ~ 400 kg of 136Xe

Enrichment of isotopes

82Se: 100 kg in 3 years in ECP Zelenogorsk (Siberia) price ~ 50 keuros / kgAgreement for 1.5 kg (ILIAS funding)

Enrichment by centrifugation:

• SILVA Infrastructure in Pierrelate (France)• In 2003: enrichment of 200 kg of 235U in 2 weeks !

235U + 3 photons 235U+ + e

• Possibility of enrichment of 200 kg of 150Nd in few weeks ! Simulations done par Alain Petit (DEM, CEA) • Enrichment of 96Zr and of 48Ca could be considered : to be studied…

• Main goal : maintain the installation for an enrichment of 100 kg of 150Nd “Statement” of the SuperNEMO collaboration

Enrichment by laser photoionisation

Sensibility of SuperNEMO : discussionSensibility of SuperNEMO : discussion

Simulation Monte Carlo with 5 years of data taking 82Se T1/2 > 1026 years

mais constrain on 214Bi, Radon et 208Tl are very strong

150Nd T1/2 > 6 1025 years equivalent to 5 1026 y (82Se) because of the phase space factor. background similar for 82Se whereas T1/2 is lower

(Fermi factor : coulombian effect due to the high Z) No constraint on 214Bi and radon (Q = 3.367 MeV)

48Ca T1/2 1.5 1026 years equivalent to 5 1026 y (82Se) because of the phase space factor. No constrain on 214Bi and radon Constrain on 208Tl much less stronger (Q = 4.271 MeV)

150Nd: T1/2() = 1019 y82Se: T1/2() = 1020 y

Experiment Nucleus Mass(kg)

FWHM atQ (keV)

BackgroundCounts/

fwhm.kg.y

T1/2()

limit(years)

<m> limit

(meV)

Startingtakingdata

NEMO 3

CUORICINO

100Mo82Se

130Te

71

10

350350

7

~ 0.5~ 0.1

~ 0.2

2. 1024

8. 1023

4. 1024

300 - 1300600 – 1700

250 – 850

GERDA Phase 1 Phase 2 Phase 3

76Ge 1535

300

444

0.040.0040.004

3. 1025

2. 1026

6. 1027

250 – 780100 – 290

20 – 55

2008??

SuperNEMO 82Se 150Nd

100 210 0.01 1. 1026

6. 1025

45 – 13070

20122012

CUORE

if enrichmt 130Te

natTenatTe130Te

200200700

555

0.050.0050.005

2. 1026

6.6 1026

2. 1027

35 – 120 20 – 65

2012??

CANDLES IIIif enrichmt 48Ca

natCa48Ca

0.2200

200200 0.1 4 1026 30 – 100

2007?

EXO-200EXO Ba+ tag

136Xe 1601000

5050

0.950.025

3. 1025

1027

90 – 55015 – 95

2007?

Nuclear Matrice elements: Shell Model: Caurier (2004) private com. Stoica et al. (2001) Suhonen et al. (1998 and 2003) QRPA Rodin, Simkovic, Faessler (2005)

Expected sensitivities

COBRA 116Cd 418 <56 <0.001 ~1026 ?~ 60-180

Constrain on <m>

Cosm

ology

Cosm

ology

Current experiments Current experiments

Next generation Next generation

(Figure from C. Giunti)

Cuoricino and NEMO3 are running ~ for 5 years : range ≈ a few 100 meV

R&D for new experiments with a mass of ≈ 100 kg of enriched isotopes.

aim : a few 10 meV with at least 3 isotopes

Coordination in Europe (ILIAS)

Neutrinoless double beta decay could be one of the experimental key for understanding neutrino physics : it is a long way but promising ?

ConclusionConclusion

Radon in the NEMO-3 gas of the wire chamber

Due to a tiny diffusion of the radon of the laboratory inside the detector A(Radon) in the lab ~15 Bq/m3

222Rn (3.8 days)

218Po

214Pb

214Bi

214Po

210Pb

s

~ 1 -like events/year/kg with 2.8 < E1+E2 < 3.2 MeV

Two independent measurements of radon in NEMO-3 gas

Good agreement between the two measurements

Radon detector at the input/output of the NEMO-3 gas

~ 20 counts/day for 20 mBq/ m3

(1e + 1 ) channel in the NEMO-3 data:Delayed tracks (<700 s) to tag delayed from 214Po

214Bi 214Po (164 s) 210Pb

~ 200 counts/hour for 20 mBq/m3

A(Radon) in NEMO-3 20-30 mBq/m3

Decay in gas

delayed

214Bi 214Po (164 s) 210Pb

Radon was the dominant backgroundRadon was the dominant background

for for 00 search in NEMO-3 search in NEMO-3

May 2004 : Tent surrounding the detector

Free-Radon Purification System 1/2Free-Radon Purification System 1/2

Starts running Oct. 4th 2004 in Modane Underground Lab.

1 ton charcoal @ -50oC, 7 bars

Activity: A(222Rn) < 15 mBq/m3 !!!Flux: 125 m3/h a factor 1000

Free-Radon Air Free-Radon Air factoryfactory

5.8 11.6 17.4 23.1 Time (days)

Level of radon measured inside the wire chamber, by analysing (1e + 1 ) channel in the NEMO-3 data

Without tent: A ~ 1.5 Bq

After flushing radon-free air inside the tent: A ~ 0.15 Bq

Radon level reduced by a factor of 10

Residual level to

be understood

sources ?

Thanks a lot to S.K especially M.Nakahata,S.Tasaka

Radon level inside the detectorRadon level inside the detector

- Results -- Results -

The double beta process

Allowed process2

if m0 and

double beta 0

Q: end-point energy ~ 2-4 MeV

Experimentally : a peak forThe energy sum of the 2 e-

Arbitrary

scale

E/Q

Two different approachesPURE CALORIMETER

• only measurement ofthe energy sum of the 2 e-

Esum• high efficiency• high precision for the

measurement of EsumBUT

• sensitive to an unknown gamma line

Semi-conductors : GERDA,MAJORANA (Ge)

CANDLE (Cd,Te)Bolometer :

CUORICINO/CUORE

TRACKING+CALORIMETER• identification of the 2 e-

• measurement of the 2 electrons energies, and of the angular distribution

• measurement of each background amount

BUT• reduced efficiency andenergy resolution

NEMO/SuperNEMO, EXO

IDENTIFICATION OF THE NATURE OF THE PROCESS(Majorana , right current…)

GERDA : 76Ge in LNGS

Vacuum insulated Copper or steel vessel

Water tank / buffer/ muon veto

Liquid N/Ar

Ge Array

Phase I :17.9 kg of enriched

Ge-detectors underground at LNGS

(from IGEX and Heidelberg-Moscow)

HdM

IGEX