Experimental status of the Double Beta Decay Marisa Pedretti INFN Milano Bicocca.

Experimental status of the

Double Beta Decay

Marisa Pedretti

INFNMilano Bicocca

Marisa Pedretti - INFN Physics of Massive Neutrinos, Blaubeuren

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OUTLOOK OF THIS TALKOUTLOOK OF THIS TALK OUTLOOK OF THIS TALKOUTLOOK OF THIS TALK

- Neutrinoless Double Beta Decay and Neutrino Physics

- Requirements for a competitive experiment

- Present situation of 0DBD

- Future experiments


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two electrons each with a continuous spectrum and a monochromatic sum energy

new physics beyond the SM

Double Beta Decay SignatureDouble Beta Decay Signature Double Beta Decay SignatureDouble Beta Decay Signature

0DBD: (A,Z) (A,Z+2) + 2e-

2DBD: (A,Z) (A,Z+2) + 2e- + 2

e Allowed by SM

sum electron energy / Q

2 neutrinos Double Beta Decay continuous spectrum

Neutrinoless Double Beta Decaypeak enlarged by the detector

energy resolution


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00DBD and neutrino physicsDBD and neutrino physics 00DBD and neutrino physicsDBD and neutrino physics

parameter containing the physics

what the nuclear theorists try to calculate

what the experimentalists try to measure

How 0DBD is connected to neutrino mixing matrix and masses?

M = ||Ue1 | 2M1 + ei | Ue2 | 2M2 + ei |Ue3 | 2M3 |

= G(Q,Z) |Mnucl|2M 2

neutrinolessDouble Beta Decay

rate

Phase space

Nuclear matrix elements Effective

Majorana mass

In case of dominant mass mechanism:


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M = ||Ue1 | 2M1 + ei | Ue2 | 2M2 + ei |Ue3 | 2M3 |

00DBD and neutrino physicsDBD and neutrino physics 00DBD and neutrino physicsDBD and neutrino physics

S. Pascoli, S. T. Petcov and T. Schwetz, hep-ph/0505226

76Ge claim

excluded by CUORICINO , NEMO3

Inverted Hierarchy

Normal Hierarchy

Quasi Degenerate


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Target sensitivity Target sensitivity Target sensitivity Target sensitivity


Approach the inverted hierarchy region in a first phase (m>50 meV)

Exclude the inverted hierarchy region in a second phase (m>15 meV)

Future target sensitivities can be divided in two phases:


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15 meV

50 meV

500 meV

3 different value of neutrino mass can be seen as future milestones:


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In order to give an idea of the amazing challenge of the future sensitivity targhet:



15 meV

50 meV

500 meV

Counts / y ton Ge natural

Ge enriched

TeO2 natural

TeO2 enriched

Rodin et al.

CivitareseSuhonen

new calculation 50 599 411 1085

1519Nucl. Phys. A

729, 867 (2003)

37 434 575


Ge enriched

TeO2 natural

TeO2 enriched

Rodin et al.new calculation

CivitareseSuhonen

Nucl. Phys. A 729, 867 (2003)

0.51 5.99 4.11 10.85

0.37 4.3 5.7 15

new calculation


Ge enriched

TeO2 natural

TeO2 enriched

Rodin et al.

CivitareseSuhonen

Nucl. Phys. A 729, 867 (2003)

0.046 0.54

0.033 0.39

0.37 0.98

0.52 1.37Sensitive masses at the 1 ton scale are requiredThe order magnitude of the Bkg is ≤ 1 c / y ton


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Experimental parametersExperimental parameters Experimental parametersExperimental parametersHow experimental parameters are connected to the

Majorana mass sensitivity of experiment?

sensitivity F: lifetime corresponding to the minimum detectable number of events over background at a given confidence level

background level

F (MT / bE)1/2

energy resolutionlive timesource mass

F MT

importance of the nuclide choice(but large uncertainty due to nuclear physics)

sensitivity to m (F/Q |Mnucl|2)1/2 1 bE

MT Q1/2

1/4

|Mnucl|

b 0 b = 0b: specific background coefficient

[counts/(keV kg y)]


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Background SourcesBackground Sources Background SourcesBackground Sources

Common to all tecnhiques

and experiments

Cooperation(in Europe, ILIAS)

Natural radioactivity of materials (source itself, surrounding structures)

Neutrons

Cosmogenic induced activity (long living)

2 Double Beta Decay

Levels of < 1 Bq / kg are required for some materials at the ton scale

Purification techniques

Quality control procedure to establish:diagnostic is a problem by itself (traditional gamma counting not sufficient)Improve alternative techniques:- ICPMS- Neutron Activation Analysis- “Ad hoc” bolometers for alpha self-counting- Full prototype used to measure contamination (BiPo detector)

Two main sources

- Activity in the rock and in surrounding materials (, n) processes [0,10] MeV spectrum can be shielded

- High-energy induced complicated problem depth appropriate shielding / coincidence techniques reliable simulations “Ad hoc” experiments at muon accelerators could be useful

Choice of materials

Storage of materials underground

Partial or full detector realization underground(Ge diodes)

Crucial for all experiments and

techniques

cooperation (in Europe, ILIAS)

Critical in the low energy resolution techniques

10-4

10-3

10-2

10-1

100

101

102

103

<m

>

Sen

sit

ivit

y(m

eV

)

54321Resolution (%)

100Mo

136Xe

76Ge

130Te

energy resolution [%]

1000

100

10

1

0.1

0.01

0.001

sen

siti

vity

to

m [

meV

]

1 2 3 4

present sensitivity

Inverted hierarchy

A challenge for the space-resolving techniques,which normally have low energy resolution (~ 10 %)


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Choice of the nuclideChoice of the nuclide Choice of the nuclideChoice of the nuclideIsotopic abundance (%)

48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd

0

20

40

Transition energy (MeV)

48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd

2

3

4

5

end of region

Nuclear Matrix Element

new calculation


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High energy resolution (<2%)No tracking capabilityEasy to reject 2DBD background

Low energy resolution (>2%)Tracking / topology capabilityEasy to approach zero backround

(with the exception of 2 DBD component)

e-

e-

Source DetectorEasy to approach the ton scale

e-

e-

source

detector

detector

Source DetectorEasy to get tracking capability

Experimental techniques Experimental techniques Experimental techniques Experimental techniques

CUORE - 130TeArray of low temperature natural TeO2 calorimeters operated at 10 mKFirst step: 200 Kg (2011) – LNGS Proved energy resolution: 0.25 % FWHMGERDA - 76GeArray of enriched Ge diodes operated in liquid nitrogen or liquid argonFirst phase: 18 Kg; second phase: 40 Kg - LNGSProved energy resolution: 0.16 % FWHMMAJORANA - 76GeArray of enriched Ge diodes operated in conventional Cu cryostatsBased on 60 Kg modules; first step: 2x60 Kg modulesProved energy resolution: 0.16 % FWHMCOBRA - 116Cd competing candidate – 9 isotopesArray of 116Cd enriched CdZnTe of semiconductor detectors at room temperaturesFinal aim: 117 kg of 116CdSmall scale prototype at LNGSProved energy resolution: 1.9% FWHM

Even though these experiments do not have tracking capability, some space information helps in reducing the background thanks to:GRANULARITY of the basic design- CUORE: 988 closed packed individual bolometers- COBRA: 64,000 closed packed individual detectors- MAJORANA: 57 closed packed individual diodes per modulePULSE SHAPE DISCRIMINATION- GERDA / MAJORANA can separate single / multi site eventsSEGMENTATION and PIXELLIZATIONGranularity can be achieved through electrodes segmentation R&D in progress for GERDA, MAJORANA, COBRASURFACE SENSITIVITY in bolometers- R&D in progress in CUORE against energy-degraded and backgroundSimultaneous LIGHT and PHONON detection in bolometers- R&D in progress in CUORE-like detectors for / rejection


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e-

e-


e-

e-

source

detector

detector


High energy resolution (<2%)No tracking capability

Easy to reject 2 DBD background

Low energy resolution (>2%)Tracking capabilityEasy to approach zero backround


SUPERNEMO - 82Se or 150NdModules with source foils, tracking and calorimetric sections, magnetic field for charge signPossible configuration: 20 modules with 5 kg source for each module 100 KgEnergy resolution: 4 % FWHMMOON - 100Mo or 82Se or 150NdMultilayer plastic scintillators interleaved with source foils + tracking section MOON-1 prototype without tracking section Proved energy resolution: 6.8 % FWHMFinal target: collect 5 y x tonDCBA - 82Se or 150NdMomentum analyzer for particles consisting of source foils into a drift chamber with magnetic fieldPrototype under construction: Nd2O3 foils 1.2 g of 150NdSpace resolution ~ 0.5 mm; energy resolution 11% FWHM at 1 MeV 6 % FWHM at 3 MeVFinal target: 10 modules with 84 m2 source foil for module (126 through 330 Kg total mass)



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e-

e-


e-

e-

source

detector

detector


High energy resolution (<2%)No tracking capabilityEasy to reject 2 DBD background



EXO – 136XeTPC of enriched liquid XenonEvent position and topology; in prospect, tagging of Ba single ion (DBD daughter) only 2DBD backgroundNext step (EXO-200: funded, under construction): 200 kg – will be operated in the WIPP facilityProved energy resolution: 3.3 % FWHM



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e-

e-


e-

e-

source

detector

detector


High energy resolution (<2%)No tracking capabilityEasy to reject 2 DBD background



SNO++ – 150NdLiquid scintillator loaded with Nd1000Ton in SNO detector. Total isotope mass 560 kg. Probable energy resolution: 6.7 % FWHMThis experiment compensates the low energy resolution with the huge statistic



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Source = DetectorWell known Ge diodes technology

5 Ge diodes with a total statistic of 10.9 kg - ( 86%) 76Ge location: Underground Gran Sasso Laboratory (Italy) detectors shielded with lead and N2 fluxed Reduction of Bkg with Pulse Shape Analysis (PSA) (factor 5)

Multi-site events identification (gamma bkg)7.6 1025 76Ge nuclei

Heidelberg Moscow Exp and the 0Heidelberg Moscow Exp and the 0DBD DBD claim claim Heidelberg Moscow Exp and the 0Heidelberg Moscow Exp and the 0DBD DBD claim claim December 2001, 4 authors (KDHK) of HM collaboration claim the 0DBD of

76Ge

Spectrum with 71.7 kg•y


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KKDC claim: mee = 0.1 - 0.9 eV (0.44 eV b.v.)

1/20 (y) = (0.69 – 4.81) 1025 y (1.19

1025 y b.v.) (99,9973 % c.l. 4.2 σ) H.V. Klapdor-Kleingrothaus et al. NIM. A 522(2004)371

most probable value:28.7 in 71.7 kg y exposition

Skepticism of scientific community

Klapdor-Kleingrothaus HV hep-ph/0205228H.L. Harney, hep-ph/0205293 Independent answers of authors

Klapdor-Kleingrothaus HV et al., NIM A510(2003)281Klapdor-Kleingrothaus et al., NIM A 522(2004)371 Other articles

Aalseth CE et al. , Mod. Phys. Lett. A 17 (2002) 1475Feruglio F et al. , Nucl. Phys. B 637 (2002) 345Zdezenko Yu G et al., Phys. Lett. B546(2002)206

Comments and analysis HD-M data

Heidelberg Moscow Exp and the 0Heidelberg Moscow Exp and the 0DBD DBD claim claim Heidelberg Moscow Exp and the 0Heidelberg Moscow Exp and the 0DBD DBD claim claim

Not totally accepted result • unrecognized peaks

• dimension of analyzed energy window


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ExperimentsExperimentsFrom the ApPEC roadmap…


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Running experiments

Running experiments


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NEMO 3 NEMO 3 (Neutrino Ettore Majorana Experiment)(Neutrino Ettore Majorana Experiment) NEMO 3 NEMO 3 (Neutrino Ettore Majorana Experiment)(Neutrino Ettore Majorana Experiment)

Other sources

→ 100MoQ = 3034 keV

Detector: tracking detector with different sources

Energy resolution: 8% @ QvalueLocation: Modane Underground Laboratory (France)

Bckg

sourcesthicknessmg/cm2)

82Se (0,93 kg)

Multi-source detector


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1 Source plane

2 Tracking volume (3-D readout wire drift

chamber with 6180 cells)

3 Calorimeter volume (1940 plastic

scintillator block)

2spectrum

Vertex

event

E1+E2= 2088 keV t= 0.22 ns(vertex) = 2.1 mm

E1

E2

e-

e-


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1 Source plane

2 Tracking volume (3-D readout wire drift

chamber with 6180 cells)

3 Calorimeter volume (1940 plastic

scintillator block)

bkg ~ 0.3 c/y/kg [2.8-3.2] MeV

1/20 (y) > 5.8 1023 y (90% CL)

mee < 0.64 – 2.4 eV

Present limit on 100Mo 0DBD

1/20 (y) ~ 2 1024 y

mee ~ 0.3 – 1.3 eV

Expected sensitivity @ end 2009


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Cuoricino ExperimentCuoricino Experiment Cuoricino ExperimentCuoricino ExperimentHeat bathThermal coupling

Thermometer

incident particle

Crystal absorber

T = E/C

Thermal signal

Detector works at low temperature

→ 130TeQ = 2530 keV

Detector: array of 62 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvinEnergy resolution: 0.28% @ QvalueLocation: LNGS (Italy)

~ 34% natural abundance


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Cuoricino ExperimentCuoricino Experiment Cuoricino ExperimentCuoricino Experiment

→ 130TeQ = 2530 keV




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Cuoricino ExperimentCuoricino Experiment Cuoricino ExperimentCuoricino Experiment

→ 130TeQ = 2530 keV



bkg ~ 0.18 ± 0.01 c/keV/kg/y

1/20 (y) > 3 1024 y (90% CL)

mee < 0.2 – 0.98 eV

Present limit on 130Te 0DBD

1/20 (y) ~ 6.1 1024 y

mee ~ 0.1 – 0.6 eV

Expected sensitivity


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Future (but not so far)

experimentsFuture (but not so far)

experiments


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→ 130Te

Q = 2530 keV


CUORE CUORE (Cryogenic Underground Observatory (Cryogenic Underground Observatory for Rare Event)for Rare Event)


90

cm

Expansion of Cuoricino

19 towers Cuoricino-like

Detector: array of 988 5x5x5 cm3 TeO2 bolometers @ ~ 10 mKelvin (total mass = 741 kg)Energy resolution: 0.28% @ QvalueLocation: Hall A at LNGS (Italy)


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F0 = 9.2 1025 ( T [ y ] )1/2 F0 = 2.9 1026 ( T [ y ] )1/2

5 y sensitivity (1 ) with conservative Assumption: b = 0.01 counts/(keV kg y)

5 y sensitivity (1 ) with aggressive assumption: b = 0.001 counts/(keV kg y)

M < 20 – 100 meV M < 11 – 60 meV

Montecarlo simulations of the background show that b = 0.001 counts / (keV kg y)is possible with the present bulk contamination of detector materials

The problem is the surface background (alpha, beta energy-degraded)

it must be reduced by a factor 10 – 100 with respect to Cuoricinowork in progress! (only a factor 2 from the conservative assumption)

M < 7 – 38 meVenriched CUORE


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The GERDA ExperimentThe GERDA Experiment The GERDA ExperimentThe GERDA Experiment

→ 76GeQ = 2039 keV

Detector: Array of enriched (~86%) Ge

Good energy resolution: < 0.19% at QLocation: Hall A at LNGS (Italy), 3400 mwe

the mountain provides a passive cosmic ray reduction


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The GERDA Experiment: detectorThe GERDA Experiment: detector The GERDA Experiment: detectorThe GERDA Experiment: detector

The detectors, arranged in strings, will be put in LAr in order to cool down them and also shield them.


31

The GERDA Experiment: setupThe GERDA Experiment: setup The GERDA Experiment: setupThe GERDA Experiment: setup

Ge Array

Germanium detectors

Water / Muon-Veto (Č)

Clean room / lock

Steel-tank + Cu lining

Liquid argon (nitrogen)

- neutron moderator - Cerenkov

medium for 4 muon veto

Additional water shielding:


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The GERDA ExperimentThe GERDA Experiment The GERDA ExperimentThe GERDA Experiment

Tools for the bkg reduction:

• muon veto (Cerenkov detector)

• anticoincidence among the detectors

• pulse shape analysis

• segmented crystals• active veto with LAr scintillation


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GERDA goal and phasesGERDA goal and phases GERDA goal and phasesGERDA goal and phases

Phase II:new segmented detectors

exposure: 100 kg·y

(it was 71 kg·y in HM)

bkg: 10-3 count/(keV kg y)

Phase I: test claim8 crystals from HM and IGEX (18 Kg)

exposure: 15 kg·y

bkg: 10-2 cnt/(keV kg y)(exclude 99% c.l. or confirm 5 the 0nDBD claim)

Bkg Goal: 10-3 count/(keV kg y)improvement of a factor 100 with respect HM

claim

Further Possible PhaseCollaboration with Majorana Experiment to construct a single larger experiment

37 Kg of enriched 76Ge already bought for the construction of

2nd phase detectors


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SuperNEMO SuperNEMO SuperNEMO SuperNEMO Expansion of NEMO-3

→ 82SeQ = 2995 keV

Detector: tracking detector with different sources

→ 150NdQ = 3367 keV

Location: Modane (Fr) / Canfranc (SP)

5 m

1m

Top view

Tracking: drift chamber ~3000 cell (Gaiger mode)Calorimeter: scintillators + PM ~ 1000 if sc. blocks

~ 100 scint. bars


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Improvement with respect to NEMO-3:

SuperNEMO SuperNEMO SuperNEMO SuperNEMO

NEMO-3 SuperNEMO100Mo Choice of isotope 150Nd or 82Se

7 kg 100 -200 kg Isotope Mass

Efficiency8% 30%

Internal contamination208Tl < 20 mBq/Kg214Bi < 300 mBq/Kg

208Tl < 2 mBq/Kg214Bi < 10 mBq/Kg

Energy resolution8% @ 3MeV 4% @ 3MeV

SENSITIVITY1/2

0 (y) ~ 2 1024 y<m> ~ 0.3 -1.3 eV

1/20 (y) ~ 1026 y

<m> ~ 50 meV

Full experiment running at the end of 2012


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EXO-200 EXO-200 (Enriched Xenon Observatory)(Enriched Xenon Observatory) EXO-200 EXO-200 (Enriched Xenon Observatory)(Enriched Xenon Observatory)

→ 136Xe

Q = 2458 keV

200 kg of Xe enriched to 80% in 136

GOALS - search for 0nDBD with competitive sensitivity (and test the claim)- measure 2DBD half life (best limit currently set

by Bernabei et al. 1x1022y)- Understand the operation of a large LXe

detector • Understand bkg / characterize detectors materials• Learn about large scale Xe enrichment• Understand Xe handling, purification

Detector: TPC of enriched liquid Xenon able to reconstruct the event position and topology. In this phase the Ba tagging technique (for the reduction of the background) will not be used


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Improve energy resolution via simultaneous collection of ionized electrons and scintillation light


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EXO-200 – the LXe TPCEXO-200 – the LXe TPC EXO-200 – the LXe TPCEXO-200 – the LXe TPC

Teflon light reflector

APD planeCentral HV plane

Supporting ringX and Y plane


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In the first part of this year the cryostat has been commissioned and it has successfully liquefied 30 kg of natural Xenon

Now they are moving all their structures from Stanford to WIPP


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Low but finite radioactive background: 20 counts/year in ±2σ interval centered around the 2.458 MeV endpoint

Negligible background from 2νDBD (T1/2> 1·1022 yr R.Bernabei et al. measurement)

No Ba tagging capability

In case that the Klapdor’s claim is correct EXO-200 in 2 year will see:

- 15 events on top of 40 events of bkg in the worst case (QRPA – upper limit) -> 2- 162 events on top of 40 of bkg in the best case (NSM, lower limit) -> 11

Rodin et al Phys Rev C 68(2003)044302

Courier et al. Nucl Phys A 654 (1999) 973c


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SNO++SNO++ SNO++SNO++

→ 150Nd

Q = 3368 keV

Nd enriched to 56% in 150Detector: refill SNO detector with liquid scintillator (linear alkylbenzene - LAB) loaded at 0.1% with enriched Nd (not enough light output in SNO+ if using 1% Nd loading) 560 kg of 150Nd (compared to 37 g

in NEMO-III)

En resolution: 6.4% @ Qvalue

Location: Sudbury (Canada)


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Simulation:<mv>=150 meV1 year of data

a liquid scintillator detector has poor energy resolution; but enormous quantities of isotope (high statistics) and low backgrounds help compensate

SNO++SNO++ SNO++SNO++

- Test on stability of Nd-LAB: no change in optical properties after > 1 year- Small Nd-LS detector with , source demonstrates it works as scintillator

Sensitivityassumed background levels (U, Th) in the Nd-LS to be at the same level as KamLAND scintillator

2011: below 100 meV sensitivity reached if natural Nd and below 50 meVreached if enriched Nd


43

COBRA COBRA (CZT 0-neutrino Beta-decay Research Apparatus)(CZT 0-neutrino Beta-decay Research Apparatus) COBRA COBRA (CZT 0-neutrino Beta-decay Research Apparatus)(CZT 0-neutrino Beta-decay Research Apparatus)

→ 116Cd

Q = 2809 keV

Detector: 64000 1 cm3 CZT detectors for a total mass of 418 kg → 183 kg of interesting isotope

Enriched to 90%

Location: LNGS (Italy)


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COBRA COBRA (CZT 0-neutrino Beta-decay Research Apparatus)(CZT 0-neutrino Beta-decay Research Apparatus) COBRA COBRA (CZT 0-neutrino Beta-decay Research Apparatus)(CZT 0-neutrino Beta-decay Research Apparatus)

The collaboration has mounted the first layer of a 4x4x4 1cm3 new array (without enriched crystals) that is now running. They will complete the 64 detector array in autumn.

Resulting Energy Resolution: 1.9% @ QvaluePossibility to study the coincidence to make a Bkg reduction

R&D on pixellisation of detector electrodes (200m pixel) to make a particle ID for a Bkg reduction solid state TPC

Reduction at least of a factor 10 of Bkg (10 c/(keV Kg y)

2x2x0.5 cm3 with 64 pixels


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Future scenariosFuture scenarios Future scenariosFuture scenariosThe future scenarios can be divided in possible steps: • I step [100-500 meV]:

to test of HM claim and to probe the QD region of neutrino massSuperNEMO, CUORE, GERDA, EXO-200, SNO++

if the neutrino mass is in this range different experiment could see it with different isotopes. Precision measurement era for 0nDBD

• II step [15-50 meV]: to probe the IH region of neutrino mass. 1 ton scale and 10 y

SuperNEMO (especially with 150Nd), CUORE (especially if enriched), GERDA-III, SNO++

(enriched)discovery in 3-4 isotopes is necessary to confirm the

observation• III step [2-5 meV]: For this big leap in sensitivity new approaches are required.Next generation experiments are precious for the selection of the future approaches100 tons of isotopes Unpredictable time scale and large investment in enrichment

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Experimental status of the Double Beta Decay Marisa Pedretti INFN Milano Bicocca.

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