From CUORICINO to CUORE: From CUORICINO to CUORE: To probe the inverted hierarchy regionTo probe the inverted hierarchy region

On behalf of the CUORE collaboration DUSL Meeting, Washington DC November 2,-4, 2007

Frank Avignone University of South Carolina and INFN Laboratori Nazionali del Gran Sasso

The CUORE collaborationThe CUORE collaborationIT

ALY

UN

ITE

D S

TA

TE

S

Decay modes for Double Beta DecayDecay modes for Double Beta Decay

(A,Z) (A,Z+2) + 2e-neutrinoless Double Beta Decay (0-DBD)

never observed (except KKDK claim)> 1025 y

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

2 Double Beta Decay allowed by the Standard Model

observed : = 1019 -1021y

Electron sum energy spectra in DBDElectron sum energy spectra in DBD

The shape of the two electron sum energy spectrum enables us to distinguish between the two decay modes

sum electron energy / Q

two neutrino DBDcontinuum with maximum at ~1/3 Q

neutrinoless DBDpeak enlarged only by

the detector energy resolution

130130Te as a DBD candidateTe as a DBD candidate

high natural isotopic abundance (nat. abundance = 33.87 %)

high transition energy ( Q = 2530 keV )

encouraging theoretical matrix element

observed with geo-chemical techniques (incl = ( 7 - 27 ) 1020 y)

2 DBD decay observed by a precursor bolometric experiment (MIBETA) and by NEMO-3 at the level = (7.6 ) 1020 y

Large natural abundance Low-cost

Expandability of Double-Beta Decay experiments

€

mν = 50meV ⇒ T1/20ν ≈ 3×1026 y

The bolometric technique for The bolometric technique for 130130Te: detector conceptsTe: detector concepts

Tellurium oxide bolometers for DBDTellurium oxide bolometers for DBD

Energy absorbersingle TeO2 crystal 790 g 5 x 5 x 5 cm

Thermometer(Neutron transition doped Ge chip)

CUORICINO/CUORE LocationCUORICINO/CUORE Location

CUORICINO experiment installed in

Laboratori Nazionali del Gran SassoL'Aquila – ITALY

the mountain provides a 3500 m.w.e. shield against cosmic rays

R&D final tests for CUORE (hall C)

CUORE (hall A)

CUORICINO(hall A)

CUORICINO = tower of 13 modules, 11 modules x 4 detector (790 g) each

2 modules x 9 detector (340 g) each M = ~ 41 kg ~ 5 x 1025 130Te nuclei

The CUORICINO structureThe CUORICINO structure

Cold finger

Tower

Lead shield

Same cryostatand similar

structureas previous

pilot experiment

Coldest point

Detector performanceDetector performance

2.61.60.6Energy [MeV]

Cou

nts

(/1.

2 ke

V)

10

60 238U + 232Th calibration spectrum

208Tl

214Bi

40K

228Ac

Performance of CUORICINO detectors (555 cm3 - 790 g):

Detector base temperature: ~ 7 mK

Detector operation temperature: ~ 9 mK Detector response: ~ 250 V/ MeV

FWHM resolution: ~ 3.9 keV @ 2.6 MeV

130Te0

60Co sum peak2505 keV

~ 3 FWHM from DBD Q-value

/20 (y) > 3.0 1024 y (90% CL ) M < 0.38 – 0.58 eV

CUORICINO resultsCUORICINO results

MT = 11.83 kg 130Te y

Bkg = 0.18±0.02 c/keV/kg/y

Rodin et al. nucl-th/0706.4304Caurier et al., New Shell Model

Average FWHM resolution for 790 g detectors: 7 keV

CUORE = close-packed array of 988 detectors19 towers - 13 modules/tower - 4 detectors/moduleM = 741 kg ~ 1027 130Te nuclei

Compact structure, ideal for active shielding

From CUORICINO to CUOREFrom CUORICINO to CUORE((CCryogenic ryogenic UUnderground nderground OObservatory for bservatory for RRare are EEventsvents))

Each tower is a CUORICINO-like detector

Special dilution refrigerator

and granularity

CUORE funding and scheduleCUORE funding and schedule CUORE has a dedicated site in LNGS and construction of the site has started

The CUORE refrigerator has been funded and is on order

1000 crystals: Funding by INFN (500 already ordered) and 500 to be purchased by LLNL with US DOE funding

The CUORE Electronics: Funded in Sept. 07 by the NSF via The University of South Carolina

First CUORE tower “CUORE-0" assembled in 2008and operated in 2009 in CUORICINO Cryostat CUORE scheduled to begin in January 2011

CUORE sensitivityCUORE sensitivity

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

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

must be reduced by more than a factor of 10below that of CUORICINO: work in progress!

10 y sensitivity (1 ) with conservative Assumption: b = 0.01 counts/(keV kg y)FWHM = 10 keV

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

M < 38-58 meV

QRPA-SM

M < 23-33 meV

QRPA-SM

€

T1/20ν = 3.0 ×1026 y

€

T1/20ν = 9.2 ×1026 y

CUORE and the inverted hierarchy regionCUORE and the inverted hierarchy region

Quasi-degenarate

S. Pascoli, S.T. Petcov

Inverted hierarchy

Normal hierarchy~20 meV

~50 meV

Inverted hierarchy band

M

Lightest neutrino mass

The CUORE background modelThe CUORE background model Sources of the background

1. Radioactive contamination in the detector materials (bulk and surface)2. Radioactive contamination in the set-up, shielding included3. Neutrons from rock radioactivity4. Muon-induced neutrons

Monte Carlo simulation of the CUORE background based on:

1. CUORE baseline structure and geometry2. Gamma and alpha counting with HPGe and Si-barrier detectors 3. CUORICINO experience CUORICINO background model4. Specific measurements with dedicated bolometers in test DR in LNGS

Results…..

The CUORE background componentsThe CUORE background components

ComponentBackground in DBD region

( 10-3 counts/keV kg y )

Environmental gamma

Apparatus gamma

Crystal bulk

Crystal surfaces

Close-to-det. material bulk

Close-to-det. material surface

Neutrons

Muons

< 1

< 1

< 0.1

< 3

< 1

~ 20 – 40

~ 0.01

~ 0.01

The only limiting factor

(A) Passive methods surface cleaning

(B) Active methods ( “reserve weapons” and diagnostic) events ID

Mechanical action

Chemical etching / electrolitic processes

Surface passivation

Strategies to control surface background Strategies to control surface background

surface sensitive bolometers

scintillating bolometers able to separate from electrons

Can CUORICINO challange the KKDK claim of evidence?

T1/20v (y) = (0.91-3.6) 1025 (3σ range)

mββ= 0.23 – 0.51 eV (3σ range)

Klapdor-Kleingrothaus et al.Modern Physics Letters A21(2006) 1547.

Best value: 2.23x1025 y

Nuclear matrix element of Rodin et al., Erratum

nucl-th/0706.4304

CUORICINO and the KKDK claim of evidenceCUORICINO and the KKDK claim of evidence

Evidence of decay of 76Ge claimed by a subset of the Heidelberg-Moscow collaboration (Klapdor-Kleingrothaus et al.)

€

0νββ −

T1/20v

(Klapdor et al.)T1/2

0v (130Te)Choose a nuclear model

Compare experiments with different isotopes Compare experiments with different isotopes

QRPA Tuebingen-Bratislava -Caltech group: erratum: nucl-th/0706.4304

Civitarese and Suhonen: Nucl. Phys. A 761(2005) 313.

Shell Model: E. Caurier et al., nucl-th:0709.0277

€

FN ≡ G0ν M 0ν 2

€

T1/20ν (130Te ) =

T1/20ν (76Ge)Klapdor

FN (130Te ) / FN (76Ge)

Use three recent nuclear structure models:

KKDK DISCOVERY RANGE:

€

T1/20ν (76Ge) = (0.9 − 3.6)×1025 y

CUOICINO 90%LOWER BOUND

€

T1/20ν (130Te ) = 3×1024 y

CUORICINO SENSITIVITY

€

T1/20ν (130Te ) = 4.6 ×1024 y

DISCOVERY RANGE IS Te-130 EQUIVELENT Ranges:

€

(1.4 − 5.4)×1024 y −(Shell − Model),Caurier _ etal

€

(1.2 − 4.9)×1024 y −Civitarese & Suhonen(QRPA )

€

(2.3− 9.1)×1024 y − Rodin.et.al.(QRPA )

ConclusionsConclusions

Bolometers represent a well established technique, very competitive for neutrinoless DBD search

CUORICINO and NEMO-3 are presently the most sensitive 0DBD running experiments, with chance to confirm the HM claim of evidence if this is correct

CUORICINO demonstrates the feasibility of a large scale bolometric detector (CUORE) with good energy resolution and background

CUORE is a next generation detector; it is funded and is scheduled to begin operation in January 2011

Recent results on background suppression confirm the capability to explore the inverted hierarchy mass region with CUORE