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From Cuoricino to CUORE: From Cuoricino to CUORE: towards the inverted hierarchy regiontowards the inverted hierarchy region
Andrea Giuliani
On behalf of the CUORE collaboration
University of Insubria (Como) and INFN Milano-Bicocca
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
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 a discussed claim)
> 1025 y
(A,Z) (A,Z+2) + 2e- + 2e
2 Double Beta Decay allowed by the Standard Modelalready observed – 1019 y
Two decay modes are usually discussed:
Double Beta Decay is a very rare, second-order weak nuclear transitionwhich is possible for a few tens of even-even nuclides
Process would imply new physics beyond the Standard Model
violation of lepton number conservation
m 0
Observation of 0-DBD
Electron sum energy spectra in DBDElectron sum energy spectra in DBD
The shape of the two electron sum energy spectrum enables todistinguish among the two different discussed decay modes
sum electron energy / Q
two neutrino DBDcontinuum with maximum at ~1/3 Q
neutrinoless DBDpeak enlarged only by
the detector energy resolution
Experimental approaches to direct searchesExperimental approaches to direct searches
Two approaches for the detection of the two electrons:
e-
e-
Source Detector(calorimetric technique)
scintillation solid-state devices gaseous detectors cryogenic macrocalorimeters (bolometers)
No or scarce background identificationHigh efficiency
Energy resolution
e-
e-
source
detector
detector
Source Detector
scintillation gaseous TPC gaseous drift chamber with magnetic field and calorimetry
Event reconstructionLow efficiency
Low energy resolution
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
Properties of Properties of 130130Te as a DBD emitterTe as a DBD emitter
high natural isotopic abundance (I.A. = 33.87 %)
high transition energy ( Q = 2530 keV )
encouraging theoretical calculations for 0DBD lifetime
already observed with geo-chemical techniques (incl = ( 0.7 - 2.7 ) 1021 y)
2 DBD decay observed by a precursor bolometric experiment (MIBETA) and by NEMO3 at the level = ( 5 - 7 ) 1020 y
excellent feature for reasonable-cost expansion of Double Beta Decay experiments
large phase space, lower background
(clean window between full energy and Compton edge
of 208Tl photons)
M 50 meV 2x1026 y
130Te features as a DBD candidate:
The bolometric technique for The bolometric technique for 130130Te: detector conceptsTe: detector concepts
Temperature signal: T = E/C 0.1 mK for E = 1 MeV Bias: I 0.1 nA Joule power 1 pW Temperature rise 0.25 mK Voltage signal: V = I dR/dT T V = 1 mV for E = 1 MeV
Noise over signal bandwidth (a few Hz): Vrms = 0.2 V
Signal recovery time: = C/G 0.5 s
In real life signal about a factor 2 - 3 smaller
Energy resolution (FWHM): 1 keV
Heat sinkT 10 mK
Thermal couplingG 4 nW / K = 4 pW / mK
ThermometerNTD Ge-thermistor
R 100 MdR/dT 100 k
Energy absorberTeO2 crystal
C 2 nJ/K 1 MeV / 0.1 mK
Te dominates in mass the compoundExcellent mechanical and thermal properties
A physical realization of bolometers for DBDA physical realization of bolometers for DBD
Energy absorbersingle TeO2 crystal 790 g 5 x 5 x 5 cm
Thermometer(doped Ge chip)
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
Cuoricino and CUORE LocationCuoricino and CUORE Location
Cuoricino experiment is 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) eachM = ~ 41 kg ~ 5 x 1025 130Te nuclides
The CUORICINO set-upThe CUORICINO set-up
Cold finger
Tower
Lead shield
Same cryostatand similar
structureas previous
pilot experiment
Coldest point
Technical results on detector performancesTechnical results on detector performances
2.61.60.6Energy [MeV]
Cou
nts
(/1.
2 ke
V)
10
60 238U + 232Th calibration spectrum
208Tl
214Bi
40K
228Ac
Performance of CUORICINO-type 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% c.l.) M < 0.20 – 0.98 eV
CUORICINO physics resultsCUORICINO physics results
MT = 11.83 kg 130Te y
Bkg = 0.18±0.02 c/keV/kg/y
Compilation of NME contained in Rodin et al. Nucl. Phys. A 2006
Average FWHM resolution for 790 g detectors: 7 keV
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
CUORE = closely packed array of 988 detectors19 towers - 13 modules/tower - 4 detectors/moduleM = 741 kg ~ 1027 130Te nuclides
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
CUORE funding and scheduleCUORE funding and schedule
CUORE has a dedicated site in LNGS and the construction will start soon
The CUORE refrigerator is fully funded and has already been ordered
1000 crystals are fully funded by INFN and DoE
The first CUORE tower will be assembled in 2008 and operated in 2009
CUORE data taking is foreseen in 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 detector materials
The problem is the surface background (energy-degraded alpha, beta )
It must be reduced by more than a factor 10with respect to Cuoricino: work in progress!
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)FWHM = 10 keV
5 y sensitivity (1 ) with aggressive assumption: b = 0.001 counts/(keV kg y)FWHM = 5 keV
M < 20 – 100 meV M < 11 – 60 meV
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
The CUORE background modelThe CUORE background model
The 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 detectors in test refrigerator 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
The Cuoricino background The Cuoricino background and the surface radioactivity modeland the surface radioactivity model
214Bi
60Co p.u.
208Tl~ 0.11 c / keV kg y
Gamma region
Reconstruction of the Cuoricino spectrum Reconstruction of the Cuoricino spectrum in the region 2.5 – 6.5 MeV in the region 2.5 – 6.5 MeV
0DBD
Additional component required
here
The additional component: The additional component: inert material surface contamination inert material surface contamination
In order to explain the 2.0 - 4 MeV region BKG, one has to introduce 238U or 210Pb surface contamination of the copper structure facing the detectors
(A) Passive methods surface cleaning
(B) Active methods ( “reserve weapons” and diagnostic) events ID
Mechanical action
Chemical etching / electrolitical processes
Passivation
Strategies for the control of the surface backgroundStrategies for the control of the surface backgroundfrom inert materials from inert materials
surface sensitive bolometers
② scintillating bolometers able to separate from electrons
Claudia Nones’ talkin DM parallel section
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
Can Cuoricino scrutinize the HM claim of evidence?
T1/20v (y) = (0.69-4.18) 1025 (3σ range)
mββ= 0.24 – 0.58 eV (3σ range)
Klapdor et al.Physics Letters B 586 (2004) 198-212
Best value: 1.19x1025 y
Nuclear matrix element of Muto-Bender-Klapdor
Cuoricino and the HM claim of evidenceCuoricino and the HM claim of evidence
Evidence of 0DBD decay claimed by a part of the Heidelberg-Moscow experiment (Klapdor et al.) in the nuclide 76Ge
T1/20v
(Klapdor et al.)T1/2
0v (130Te)Choose a nuclear model
Comparison of experimental results in a given nuclear modelComparison of experimental results in a given nuclear model
2
0
0
0
0
02/11300
2/1
76
130
76
130
)()(
v
Ge
v
Te v
Ge
v
Te
vv
M
M
G
G
KlapdorTTeT
(T01/2)-1 = G0 |M0|2 M 2
QRPA Tuebingen-Bratislava -Caltech group: erratum of nucl-th/0503063
QRPA Jyväskylä group: nucl-th/0208005
Shell Model: Poves’ talk @ 4th ILIAS Annual Meeting - Chambery
For the nuclear models, consider three active schools of thoughts:
C. Nones, talk at. DBD06 Workshop, ILIAS-WG1, Valencia, April 2006
0
1
2
3
4
0 2 4 6 8 10 12T1/2 x 1024 y for 130Te
QRPA Jyväskylä et al.
Shell model
QRPA Tuebingen et al.
Cuoricino and the Cuoricino and the 7676Ge claim of evidenceGe claim of evidence
7x1024 yFinal sensitivity
3x1024 yPresent limit
The HM claim half life range (3) is converted into a corresponding range for 130Te using the three mentioned models
Nu
cle
ar
mo
de
ls
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
CUORE and the inverted hierarchy regionCUORE and the inverted hierarchy region
M band corresponding to the inverted hierarchy
band of 130Te half lives
Nuclear models
0
1
2
3
4
0 5 10 15 20 25 30 35T1/2 x 1026 y for 130Te
QRPA Tuebingen et al.
Shell Model
QRPAJyväskylä et al.Nu
cle
ar
mo
de
ls
CUORE_conservative(5 y)
CUOREAggressive
(5 y)
Double Beta Decay: physics and experimental issues
130Te and bolometers
Structure of Cuoricino and present results
From Cuoricino to CUORE
The background: model, investigation and solution
Outline of the talkOutline of the talk
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions
ConclusionsConclusions
Bolometers represent a well established technique, very competitive for neutrinoless DBD search
Cuoricino is presently the most sensitive 0DBD running experiment, with a high chance to confirm the HM claim of evidence if this is correct
Cuoricino demonstrates the feasibility of a large scale bolometric detector (CUORE) with high energy resolution and competitive background
CUORE, a next generation detector, is funded and will start to take data in 2011
Recent results on background suppression confirm the capability to start to explore the inverted hierarchy mass region