1. From Cuoricino to CUORE: approaching the inverted hierarchy region
Andrea Giuliani
University of Insubria (Como) and INFN Milano-Bicocca
On behalf of the CUORE collaboration

2. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

3. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

4. Decay modes for Double Beta Decay
Double Beta Decay is a very rare, second-order weak nuclear transition
which is possible for a few tens of even-even nuclides
(A,Z)  (A,Z+2) + 2e-
neutrinoless Double Beta Decay (0n-DBD)
never observed (except a discussed claim)
t > 1025 y 
(A,Z)  (A,Z+2) + 2e- + 2ne
2n Double Beta Decay
allowed by the Standard Model
already observed – t  1019 y 
Two decay modes are usually discussed:
Process  would imply new physics beyond the Standard Model
violation of lepton number conservation
mn  0
n  n
Observation of 0n-DBD

5. Electron sum energy spectra in DBD
The shape of the two electron sum energy spectrum enables to
distinguish among the two different discussed decay modes
sum electron energy / Q
two neutrino DBD
continuum with maximum at ~1/3 Q
neutrinoless DBD
peak enlarged only by
the detector energy resolution

6. Experimental approaches to direct searches
Two approaches for the detection of the two electrons: e-
source
detector
Source  Detector 
scintillation
gaseous TPC
gaseous drift chamber
with magnetic field and
calorimetry
Event reconstruction
Low efficiency
Low energy resolution e-
Source  Detector
(calorimetric technique) 
scintillation
solid-state devices
gaseous detectors
cryogenic macrocalorimeters
(bolometers)
No or scarce background identification
High efficiency
Energy resolution

7. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

8. Properties of 130Te as a DBD emitter
130Te features as a DBD candidate:
large phase space,
lower background
(clean window between full energy and Compton edge
of 208Tl photons)
excellent feature for reasonable-cost
expansion of Double Beta Decay experiments
high natural isotopic abundance (I.A. = %)
high transition energy ( Q = 2530 keV )
encouraging theoretical calculations for 0n-DBD lifetime
already observed with geo-chemical techniques
( t 1/2 incl = ( )  1021 y)
2n DBD decay observed by a precursor bolometric experiment (MIBETA)
and by NEMO3 at the level t 1/2 = ( )  1020 y
Mbb  50 meV  t  2x1026 y

9. The bolometric technique for 130Te: detector concepts
Heat sink
T  10 mK
Thermal coupling
G  4 nW / K = 4 pW / mK
Thermometer
NTD Ge-thermistor
R  100 MW
dR/dT  100 kW/mK
Energy absorber
TeO2 crystal
C  2 nJ/K  1 MeV / 0.1 mK
Te dominates in mass the compound
Excellent mechanical and thermal properties
Temperature signal: DT = 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: DV = I  dR/dT  DT  DV = 1 mV for E = 1 MeV
Noise over signal bandwidth (a few Hz): Vrms = 0.2 mV
Signal recovery time: t = C/G  0.5 s
In real life signal about
a factor smaller
Energy resolution (FWHM):  1 keV

10. A physical realization of bolometers for DBD
Energy absorber
single TeO2 crystal
790 g
5 x 5 x 5 cm
Thermometer
(doped Ge chip)

11. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

12. Cuoricino and CUORE Location
Cuoricino experiment was installed in
Laboratori Nazionali del Gran Sasso
L'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)

13. The CUORICINO set-up CUORICINO = tower of 13 modules,
Cold finger
Tower
Lead shield
Same cryostat
and similar
structure
as previous
pilot experiment
Coldest point
The CUORICINO set-up
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 Te nuclides

14. Technical results on detector performance
Performance of CUORICINO-type detectors (555 cm g):
Detector base temperature: ~ 7 mK
Detector operation temperature: ~ 9 mK
Detector response: ~ 250 mV/ MeV
FWHM resolution: ~ MeV
238U + 232Th calibration spectrum 60
214Bi
Counts (/1.2 keV)
228Ac
40K
208Tl 10
0.6
1.6
2.6
Energy [MeV]

15. t1/20n (y) > 3.1  1024 y (90% c.l.) CUORICINO results
60Co sum peak
2505 keV
~ 3 FWHM from DBD Q-value
MT = kg 130Te  y
Bkg = 0.18±0.02 c/keV/kg/y
130Te
0nbb
t1/20n (y) > 3.1  1024 y (90% c.l.)
Mbb < 0.20 – 0.68 eV

16. CUORICINO was stopped and disassembled
 Leave room to a crucial test to compare three different procedures to control Cu surface radiaoctivity

17. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

18. From CUORICINO to CUORE (Cryogenic Underground Observatory for Rare Events)
CUORE = closely packed array of 988 detectors
19 towers - 13 modules/tower - 4 detectors/module
M = 741 kg  ~ Te nuclides
Compact structure, ideal for active shielding
Each tower is a CUORICINO-like detector
Special dilution refrigerator

19. The CUORE collaboration

20. CUORE funding and schedule
CUORE has a dedicated site in LNGS and the hut construction has started
The CUORE refrigerator is fully funded and has already been ordered
1000 crystals are fully funded by INFN and DoE – first batch in Nov 2008
The first CUORE tower (CUORE-0) will be assembled and operated in 2009
CUORE data taking is foreseen in 2012

21. CUORE sensitivity Mbb < 11 – 60 meV Mbb < 20 – 100 meV
Montecarlo simulations of the background show that
b ~ 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 10
with respect to Cuoricino: work in progress!
F0n = 9.2 ´ 1025 ´ ( T [ y ] )1/2
F0n = 2.9 ´ 1026 ´ ( T [ y ] )1/2
5 y sensitivity (1 s) with conservative
Assumption: b = 0.01 counts/(keV kg y)
FWHM = 10 keV
5 y sensitivity (1 s) with aggressive
assumption: b = counts/(keV kg y)
FWHM = 5 keV
Mbb < 20 – 100 meV
Mbb < 11 – 60 meV

22. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

23. The CUORE background model
Monte Carlo simulation of the CUORE background based on:
CUORE baseline structure and geometry
Gamma and alpha counting with HPGe and Si-barrier detectors
Cuoricino experience  Cuoricino background model
Specific measurements with dedicated detectors in test refrigerator in LNGS
Results…..

24. The CUORE background components The only limiting factor
Background in
DBD region
( 10-3 counts/keV kg y )
Ratio to
minimal goal
Component
214Bi
60Co sum
208Tl
~ 0.1 c / keV kg y
CUORICINO Background
Environmental gamma
< 1
< 0.1
Apparatus gamma
< 1
< 0.1
Crystal bulk
The only limiting factor
< 0.1
< 0.01
Crystal surfaces
< 3
< 0.3
Close-to-det. material bulk
< 1
< 0.1
Close-to-det. material surface
~ 20 – 40
~ 2 – 4
Neutrons
~ 0.01
~ 0.001
Muons
~ 0.01
~ 0.001

25. Strategies for the control of the surface background
from inert materials
(A) Passive methods  surface cleaning
(B) Active methods ( “reserve weapons” and diagnostic) events ID
Mechanical action
Chemical etching / electrolitical processes / plasma cleaning
Passivation
Crucial test in progress
in the former CUORICINO location
 surface sensitive bolometers
scintillating bolometers able
to separate a from electrons

26. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

27. Can Cuoricino scrutinize the HM claim of evidence?
Cuoricino and the HM claim of evidence
Evidence of 0nDBD decay claimed by a part of the Heidelberg-Moscow experiment (Klapdor et al.) in the nuclide 76Ge
T1/20v (y) = ( )  1025 (3σ range)
Klapdor et al.
Physics Letters B 586 (2004)
Best value: 1.19x1025 y
mββ= 0.24 – 0.58 eV (3σ range)
Nuclear matrix element of Muto-Bender-Klapdor
Can Cuoricino scrutinize the HM claim of evidence?

28. Comparison of experimental results in a given nuclear model
(T0n1/2)-1 = G0n |M0n|2 Mbb 2
T1/20v
(Klapdor et al.)
Choose a nuclear model
T1/20v (130Te) 2 / 1
130 76 ) ( v Ge Te M G
Klapdor T × =
QRPA Tuebingen-Bratislava -Caltech group: erratum of nucl-th/
QRPA Jyväskylä group: nucl-th/
Shell Model: Poves’ 4th ILIAS Annual Meeting - Chambery
For the nuclear models, consider three active schools of thoughts:

29. Cuoricino and the 76Ge claim of evidence
The HM claim half life range (3s) is converted into a corresponding range for 130Te using the three mentioned models
3.1x1024 y
Present limit
Nuclear models
QRPA Tuebingen et al.
Shell model
QRPA Jyväskylä et al.
T1/2 x 1024 y for 130Te

30. CUORE and the inverted hierarchy region
Mbb
S. Pascoli, S.T. Petcov
Quasi-degenarate
Inverted hierarchy
~20 meV
~50 meV
Inverted hierarchy band
Normal hierarchy
Lightest neutrino mass

31. CUORE and the inverted hierarchy region
Mbb band corresponding to the inverted hierarchy
band of 130Te half lives
Nuclear models
T1/2 x 1026 y for 130Te
QRPA Tuebingen et al.
Shell Model
QRPAJyväskylä et al.
Nuclear models
CUORE_
conservative
(5 y)
CUORE
Aggressive
(5 y)

32. Outline of the talk 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
Cuoricino and CUORE potential according to recent nuclear calculations
Conclusions

33. Conclusions
Bolometers represent a well established technique, very competitive for
neutrinoless DBD search
Cuoricino has completed the data taking and has shown to be the most
sensitive 0n DBD experiment ever run together with HM; uncertainties in
nuclear models prevents from scrutinizing fully the 76Ge evidence claim
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 2012
Recent results on background suppression confirm the capability to start
to explore the inverted hierarchy mass region

34. BACK-UP SLIDES

35. CUORE SCHEDULE

36. CUORE-0 SCHEDULE

37. CRYOSTAT SCHEDULE

38. CALIBRATION 12 sources will be guided inside the cryostat
The source: active wire contained in copper crimp tubes, crimped onto a Kevlar string and covered by PTFE heat shrink sleeves
6 will go in between the towers and 6 between the HEX and STILL shield
4 ports on the 300K flange, each of which will host a motion control box with 3 independent sources

39. MUON VETO