1. First neutrinoless double beta decay results from CUORE-0
Università degli Studi di Milano - Bicocca
INFN di Milano - Bicocca
First neutrinoless double beta decay results from CUORE-0
L. Gironi on behalf of the CUORE collaboration
10th  M E D E X '15  meeting
Prague, June 09th - 12th, 2015 

2. Bolometers for 0νDBD Why bolometers are suitable detectors for 0νDBD ?
Parameters
Bolometers
Maximum sensitivity achievable regardless of Δ and B (zero background limit)
- Possibility to choose among all the ββ isotope
- optimization of a
- Very high detection efficiency (ε) (source=detector) ∆
Fundamental in 0νDBD studies because of the 2νDBD
- Excellent energy resolution (~5 keV at Q-value) B
In many cases it is still possible to act on it to greatly improve the sensitivity
- Q-value in low background region
- Very low background level already reached but surface contaminations

3. Energy release → ΔT→ ΔR in the thermistor → ΔV
TeO2 Bolometric Detectors
At 10 mK, energy deposited in TeO2 results in a measurable change in temperature
Energy release → ΔT→ ΔR in the thermistor → ΔV
ΔTtherm~ μK/MeV
ΔTcryst ~ 0.1 mK/MeV
ΔRtherm ~ 3 MΩ/MeV
ΔVtherm ~ 0.3 mV/MeV
130Te is one of the best candidates for 0νDBD search:
• favorable Q-value (2528 keV)
• highest isotopic abundance (~34%), no enrichment for present generation experiments
• large mass, high purity, highly reproducible detectors can be built with TeO2

4. The CUORE program Search for 0νDBD of 130Te with TeO2 bolometers
M: Scale up mass (~20x)
T: Cryogen-free dilution refrigerator
∆: Improve energy resolution
B: Reduce background (~20x)
Cuoricino
M· T (130Te) = kg.yr
B = ± c/keV/kg/y
∆ = 6.3 ± 2.5 keV FWHM
T1/2 > 2.8· 1024 y (90% C.L.)
CUORE
M· T (130Te) = 1030 kg.yr
B = 0.01 c/keV/kg/y
∆ = 5 keV FWHM
T1/2 = 9.5· 1025 y (90% C.L.)

5. Cuoricino T1/2 > 2.8 x 1024 y (90% C.L.)
62 TeO2 crystals (40.7 kg) operated at Gran Sasso ( )
T1/2 > 2.8 x 1024 y (90% C.L.)
• M· T (130Te): kg.yr
• ∆: 6.3 ± 2.5 keV FWHM
• B: ± c/keV/kg/yr
0νββ upper limit
mββ < ( ) meV
(R)QRPA - Phys.Rev. C (2008)
pnQRPA - JoP Conference series (2009)
ISM - Nucl. Phys. A (2009)
IBM-2 - Phys.Rev. C (2009)

6. Main sources of background in the ROI:
Cuoricino – Background
β/γ events
α events
Qββ
Physics data
Calibration data
Main sources of background in the ROI:
Qββ
30% Compton from 208Tl decays in cryostat
60% Degraded alphas on copper surfaces
10% Degraded alphas on crystal surfaces α

7. CUORE-0 is the first tower produced out of the CUORE assembly line.
52 TeO2 5x5x5 cm3 crystals (~750 g each)
13 floors of 4 crystals each
Total detector mass: 39 kg TeO2 (10.9 kg of 130Te)
Purpose:
Commission assembly line
Minimization of Rn exposure (Glove Box assembly)
Validate CUORE detector design
New (lighter) detector design structure
New surface cleaning technique (TECM)
Provide test bed for developing DAQ & analysis framework
Run as standalone experiment while CUORE is being constructed

8. Clean Room for Detector Assembly and Storage
CUORE/CUORE-0 – Assembly line
Clean Room for Detector Assembly and Storage
CUORE hut
Cuoricino/
CUORE-0 hut
CUORE-0 construction was carried out inside N2-flushed glove boxes in CUORE hut’s clean room.

9. CUORE/CUORE-0 – Assembly line
Semi-automatic gluing line
• Attach NTD, heater to each crystal
• Completely enclosed in N2 fluxed glove box
• Minimizes human interaction with parts
• Automatic, highly reproducible glue deposition

10. CUORE/CUORE-0 – Assembly line
Tower contruction
• Unpack ultra-cleaned copper/PTFE parts and quality- check in N2 atmosphere
• Parts and crystals for a floor transferred under vacuum to assembly glove box
• Build up tower floor-by-floor in N2 atmosphere, completed floors lowered into N2-fluxed ‘garage’
• Readout wire-strips glued to arms and attached to tower in N2 flushed glove box

11. CUORE/CUORE-0 – Assembly line
Connection to readout: Wire bonding
• All wire-bonding done in N2 flushed glove box
• Vertical bonding machine with auxiliary X-Y motion

12. and of the CUORE cleaning procedures.
CUORE/CUORE-0 – Assembly line
Tower storage
CUORE-0
with 10mK shield
CUORE
tower
The successful operation of CUORE-0 demonstrated the validity of the CUORE tower assembly line
and of the CUORE cleaning procedures.

13. CUORE-0 • Uses the old Cuoricino cryostat • Electronics from Cuoricino
• Shielding from Cuoricino
• Cooled to base T (~10 mK) Mar 2013

14. CUORE-0 – Data taking M· T (130Te): 9.8 kg· yr of 130Te
51/52 NTDs online
50/52 heaters online
Calibration data taking
Physics data taking
1st campaign
2nd campaign

15. The 5 keV CUORE goal has been reached
CUORE-0 – Calibration energy resolution
Total fit on the 2615 keV line
Distribution of energy 2615 keV
CUORE-0
Preliminary
CUORE-0
Preliminary
Exposure-weighted
Harmonic Mean FWHM
RMS of
FWHM
Cuoricino
5.8 keV
2.1 keV
CUORE-0
4.9 keV
2.9 keV
The 5 keV CUORE goal has been reached

16. Comparison of the total background spectrum in CUORE-0 and Cuoricino
CUORE-0 – Background
Comparison of the total background spectrum in CUORE-0 and Cuoricino
CUORE-0 Preliminary
MeV
[c/keV/kg/y]
eff
[%]
Cuoricino
0.110 ± 0.001
83 ± 1
CUORE-0
0.016 ± 0.001
81 ± 1
a factor ~7 reduction in the alpha continuum region
ɣs from U chain reduced with radon control
residual ɣ bkg in ROI from Th cryostat contaminations (negligible in CUORE)

17. CUORE-0 – 0νDBD analysis Total selection efficiency = (81.3 ± 0.6)%
Data processing and analysis techniques are focused to the correct reconstruction of each event
energy (optimal filtering technique) and eventually to the creation of the energy spectrum of the ROI:
Pile-up removal: multiple events in the same acquisition window are rejected
Pulse shape discrimination: events with unexpected shape are rejected
Anti-coincidence: only single crystals events are signal candidates
efficiency
[%]
error
Trigger
98.529
0.004
Pile-up and PSA
93.7
0.7
Event containment
88.4
0.09
Accidental coincidence
99.64
0.10
Total selection efficiency = (81.3 ± 0.6)%

18. 0.058 ± 0.004(stat.) ± 0.002(syst.) c/keV/kg/y
CUORE-0 – 0νDBD search
After all cuts: 233 events in ROI [ keV].
Best value fit of the 0νDBD decay rate:
Г0ν= 0.01 ± 0.12(stat.) ± 0.01(syst.) x yr-1
Background index in ROI:
0.058 ± 0.004(stat.) ± 0.002(syst.) c/keV/kg/y
CUORE-0 Preliminary
CUORE-0 Preliminary
Profile negative log-likelihood
We find no evidence for a signal and set 90% C.L. lower limit from profile likelihood:

19. CUORICINO/CUORE-0 combined limit
We combine the CUORE-0 result with the existing kg· yr of 130Te exposure from Cuoricino
CUORE-0 Preliminary
Profile negative log-likelihood
This is the most stringent limit on this half-life !

20. Extrapolation to mββ mββ < (270-650) meV CUORE-0 Preliminary
Combined half-life result as a limit on the effective Majorana neutrino mass:
mββ < ( ) meV
IBM-2 Phys. Rev. C 91, (2015)
QRPA-TU Phys. Rev. C 87, (2013)
pnQRPA Phys. Rev. C 91, (2015)
ISM Nucl. Phys. A 818, 139 (2009)
EDF Phys. Rev. Lett. 105, (2010)

21. The CUORE program Search for 0νDBD of 130Te with TeO2 bolometers
M: Scale up mass (~20x)
T: Cryogen-free dilution refrigerator
∆: Improve energy resolution
B: Reduce background (~20x)
Cuoricino
M· T (130Te): kg.yr
B = ± c/keV/kg/y
∆ = 6.3 ± 2.5 keV FWHM
T1/2 > 2.8· 1024 y (90% C.L.)
CUORE
M· T (130Te): 1030 kg.yr
B = 0.01 c/keV/kg/y
∆ = 5 keV FWHM
T1/2 = 9.5· 1025 y (90% C.L.)

22. CUORE Goals: 988 TeO2 5x5x5 cm3 crystals (~750 g each)
19 towers identical to CUORE-0 (13 floors of 4 crystals each)
total detector mass: 741 kg of TeO2 (206 kg of 130Te)
• newly designed dilution refrigerator made of low radioactivity materials
- Technologically challenging: ~1 ton of detectors at 10 mK
- Independent suspension of the detector array from the
dilution unit: smaller vibrational noise
Goals:
• build a 1-ton bolometric detector
• energy ROI: 5keV
• background level: 0.01 c/keV/kg/y
• sensitivity (90% C.L., 5 years):

23. CUORE – Background mitigation efforts
Improve shielding and radio-purity of cryostat materials
Neutron shield (18 cm PET + 2cm of H3BO3)
External lead shield (thickness >35 cm)
Low-radioactivity copper for cryostat vessels and flanges
Internal lead shield (low-radioactivity/ancient lead)
Improve radio-purity of active and inert surfaces in the detector
Ultra-pure TeO2 crystals
Cu frame optimized to reduce surface area facing the crystals
New ultra-cleaning for all Cu components:
- Tumbling
- Electropolishing
- Chemical etching
- Magnetron plasma etching

24. CUORE – Self shielding CUORE-0: All bolometers face 10 mK shield
CUORE: Only outermost crystals face 10 mK shield

25. CUORE – Status Assembly of the 19 CUORE towers is complete
Expect to deploy the array in the cryostat later this year.

26. CUORE – Status Cryostat assembled, passed 4K commissioning test
Dilution unit delivered to LNGS, able to maintain ~5mK in standalone commissioning tests
Final integration run (everything except detectors) is ongoing
Outermost shield
Cryostat Vessel Flanges
Diluition unit
Plan to start operations by end of 2015.

27. ? The CUORE program Cuoricino 2003-2008 M· T (130Te) = 19.75 kg.yr
B = ± c/keV/kg/y
∆ = 6.3 ± 2.5 keV FWHM
T1/2 > 2.8· 1024 y (90% C.L.)
CUORE
M· T (130Te) = 1030 kg.yr
B = 0.01 c/keV/kg/y
∆ = 5 keV FWHM
T1/2 = 9.5· 1025 y (90% C.L.)
CUPID …
M· T· ∆· B ≈ 0

28. CUORE Upgrade with Particle ID (CUPID)
Beyond CUORE
Next generation bolometric experiment for 0νββ searches aims to use active rejection techniques to drastically reduce the background:
CUORE Upgrade with Particle ID (CUPID)
arXiv:

29. Conclusions
TeO2 bolometers offer a well-established, competitive technique in the search for 0νDBD
CUORE-0
Achieved its energy resolution and background level goals.
Indicated CUORE sensitivity goal is within reach.
Did not find evidence of 130Te 0νDBD and after combination with CUORICINO data set the best limit to date on T1/2 of the decay.
CUORE
Assembly of the 19 CUORE towers is complete.
Commissioning of the cryogenic system and experimental infrastructure is in progress.
Plan to start operations by the end of 2015.

30. The CUORE Collaboration