1. neutrinoless Double Beta Decay on behalf of the CUORE collaboration
The CUORE experiment:
a search for
neutrinoless Double Beta Decay
Luca Gironi
on behalf of the CUORE collaboration
NEW TRENDS IN HIGH-ENERGY PHYSICS Alushta, Crimea September 3-10, 2011

2. Outline Neutrino mass Neutrinoless Double Beta Decay
Experimental approach
the bolometric technique
Cuoricino
the detector
the background
the 130Te half life limit
CUORE
status
scientific goal
Conclusion
Alushta – 6 September 2011
Luca Gironi

3. Neutrino oscillations and the neutrino mass
Neutrino oscillation experiments have convincingly established that neutrinos have mass
However, the absolute mass scale and the mass hierarchy are still not known
If neutrino has a nonzero rest mass, mass eigenstates (ν1, ν2, ν3) and weak interactions eigenstates (νe, νμ, ντ) do not necessarily have to coincide
Great interest for non-oscillation experiments able to study absolute neutrino mass scale and its nature:
β decay experiments
neutrinoless Double Beta Decay (0νDBD) experiments
cosmological observations
Alushta – 6 September 2011
Luca Gironi

4. pure kinematical effect
The neutrino mass: cosmology, single and double beta decay
Cosmology, single and 0νDBD measure different combinations of the neutrino mass eigenvalues, constraining the neutrino mass scale.
In a standard three active neutrino scenario:
incoherent sum
real neutrino
b decay
coherent sum
virtual neutrino
Majorana phases
0νDBD
αi=Majorana phases
simple sum
pure kinematical effect
cosmology
Alushta – 6 September 2011
Luca Gironi

5. Combine the informations
S [eV]
Strumia, F.Vissani
arXiv:hep-ph/ v3
The three mass scale parameters can be plot as a function of the lightest neutrino mass.
Two bands appear in each plot, corresponding to inverted and direct hierarchy.
The two bands merge in the degenerate case (the only one presently probed).
mbb [eV]
mb [eV]
Alushta – 6 September 2011
Luca Gironi

6. Primary role of neutrinoless Double Beta Decay
Neutrinoless Double Beta Decay (0νDBD):
Requires neutrino is a massive particle
Violates lepton number (ΔL=2), implies physics beyond Standard Model
Allows to investigate neutrino nature: Dirac or Majorana
2νDBD
0νDBD
Alushta – 6 September 2011
Luca Gironi

7. 0νDBD and neutrino mass
Extremely rare process (T0ν1/2 > 1024 y): 0νDBD never observed (except a discussed claim in 76Ge)
T0ν1/2 is the 0νββ half-life
G0ν(Q,Z) is the 'accurately calculable' phase space factor proportional to (Q-value)5 
M0ν is the Nuclear Matrix Element (NME), which carries a theoretical uncertainty of a factor of ~2-3 depending on the nucleus
<mββ> is effective double-beta neutrino mass
Possible for ~35 nuclei, only ~10 really interesting
Alushta – 6 September 2011
Luca Gironi

8. ββ summed e− energy spectrum
0νDBD: experimental approach
2νββ
0νββ
ββ summed e− energy spectrum
Signature: Two simultaneous electrons with summed energy Qββ, the Q-value for ββ in the isotope under study
Experimentalists measure the decay rate looking at a peak in the energy spectrum
Detector Sensitivity (S): the process half-life corresponding to the maximum signal that could be detected
η: stoichiometric coefficient
W: molecular weight of the active mass
a: isotopic abundance (i.a.)
ε: detector efficiency
T : measurement live time [y]
M : detector mass [kg]
B : background [c/keV/kg/y]
Δ : energy resolution [keV]
Alushta – 6 September 2011
Luca Gironi

9. Experimental approaches
To reach a high sensitivity:
high efficiency
(source = detector)
high i.a. or enrichment possibility
large detector mass
( kg )
very low-background
(underground, shieldings, ...)
excellent energy resolution
Some of the under construction/funded experiments:
Experiment
Isotope
Method
Resolution
(% at Qββ)
Efficiency
Background
(10-3 c/keV/kg/y)
Isotope Mass
(kg)
CUORE
130Te
bolometric
0.19
0.9
10-1
206
EXO
136Xe
liquid TPC
3.3
0.7
1-0.5
160
GERDA
76Ge
ionization
0.16
0.8
15-35
KamLAND-Zen
scintillation
9.5
NEXT
gas TPC
0.3
SNO+
150Nd
6.5
0.5
50-500
SuperNEMO
82Se
tracko-calo
4.0
7-100
Other experiment: CANDLES, Majorana, COBRA, MOON, ...
J.J. Gómez-Cadenas et al JCAP06(2011)007
Alushta – 6 September 2011
Luca Gironi

10. Experimental approaches: the bolometric technique
Among the different techniques excellent results can be obtained if source=detector
The bolometric technique offers several advantages:
Excellent energy resolution
Large source mass
High efficiency
Possibility to study all the 0νDBD isotope (cross checks)
Bolometric technique: the working principle
Crystals, cooled to ~10 mK inside a dilution-refrigerator cryostat, have such small heat capacities that single particle interactions produce measurable rises in temperature.
C = heat capacity
G = thermal conductance
Alushta – 6 September 2011
Luca Gironi

11. High natural abundance (i.a. 130Te ~ 34%): no need for enrichment
130Te as 0νDBD candidate
130Te
High natural abundance (i.a. 130Te ~ 34%): no need for enrichment
Q-value at ~2528 keV is above the energy range of most naturally occurring γ rays
TeO2 crystals
favorable characteristics of these crystals if compared with Te:
higher Debye temperature
rather good mechanical properties and it is possible to grow large crystals
good intrinsic radiopurity (< 1 pg/g in 232Th and 238U)
Alushta – 6 September 2011
Luca Gironi

12. Observatory for Rare Events
Evolution of the bolometric technique
All are cryogenic bolometer experiments searching for 0νDBD decay in 130Te
Cuoricino
CUORE-0
CUORE
Cryogenic Undergound
Observatory for Rare Events
11 kg 130Te
11 kg 130Te
206 kg 130Te
Alushta – 6 September 2011
Luca Gironi

13. Laboratori Nazionali del Gran Sasso (LNGS), Italy
LNGS underground facility
Laboratori Nazionali del Gran Sasso (LNGS), Italy NE
CUORE hut
Cuoricino/
CUORE-0 hut
Underground facility
Average depth ~ 3650 m.w.e.
Factor 106 reduction in muon flux to ~ 3×10—8 μ/(s·cm2)
Alushta – 6 September 2011
Luca Gironi

14. Cuoricino experiment CUORE predecessor Operated March 2003 - May 2008
62 TeO2 crystal bolometers:
44 crystals 5x5x5 cm3, (790 g)
18 crystals 3x3x6 cm3 (330 g)
14 “natural” crystals
2 enriched in 130Te (75%)
2 enriched in 128Te (82%)
40.7 kg TeO2  11.3 kg 130Te
Alushta – 6 September 2011
Luca Gironi

15. Cuoricino energy spectrum
Cuoricino single-hit background spectrum (black) and normalized 232Th calibration spectrum (red)
Degraded alpha energy tail
Gamma domain
Alpha domain
Anticoincidence cuts
0νDBD decay should produce a single-site signal 85% of the time
Excluding multi-site events reduces background by ~ 15% in the region of interest
Surface α contamination
the main source of flat background in 3-4 MeV region due to degraded α particles
Alushta – 6 September 2011
Luca Gironi

16. Cuoricino backgrounds
208Tl
214Bi
60Co
− Cuoricino single-hit background spectrum
− 232Th calibration spectrum (normalized)
There are three main sources of background in the region of interest:
~40% multi-Compton events from 2615 keV γ peak of 208Tl
~ 50% degraded alphas from 238U and 232Th on copper surfaces
~ 10% degraded alphas from 238U and 232Th on crystal surfaces
Alushta – 6 September 2011
Luca Gironi

17. Cuoricino results 130Te 0νDBD Total statistics
19.75 kg·yr 130Te exposure
130Te 0νDBD
Average energy resolution (FWHM):
Background:
130Te half-life limit:
Effective neutrino mass limit:
6.3±2.5 keV at Q-value in big crystals
0.169 ± counts/keV/kg/y
> 2.8 × 1024 y (90% C.L.)
mββ < meV
uncertainty due to N.M.E.
Alushta – 6 September 2011
Luca Gironi

18. CUORE-0 Single CUORE-like tower deliver information about backgrounds
(52 Te02 crystals chosen from CUORE crystals)
test of CUORE assembly and cleaning procedures
deliver information about backgrounds
sensitive 0νDBD experiment
same assembly procedures as CUORE
same cleaning procedure as CUORE
very similar copper frames and Teflon holder
Operated in refurbished Cuoricino cryostat
different suspension than CUORE
different shielding
CUORE-0 tower construction will start Oct. 2011
Data taking starts within 2011
Alushta – 6 September 2011
Luca Gironi

19. 741 kg TeO2 granular calorimeter
CUORE
Closely packed array of 988 TeO2 crystals (5x5x5 cm3  750 g)
- 19 towers
-13 planes each
- 4 crystals each
CUORE detector improvements
Cleaner crystals
Higher granularity (reduction alpha background due to crystal surface thanks to anticoincidence)
Cleaner copper and less per kg TeO2
Cleaner assembly environment
Copper frames less vibration-sensitive
Better self-shielding
741 kg TeO2 granular calorimeter
206 kg of 130Te
Alushta – 6 September 2011
Luca Gironi

20. CUORE CUORE cryostat improvements CUORE shieldings improvements
Cryogen-free: better duty cycle
Detector suspension independent of refrigerator apparatus
Stringent radiopurity controls on materials and assembly
CUORE shieldings improvements
Minimum lead thickess ≈ 36 cm (in Cuoricino ≈22 cm)
6 cm thick lead shield operated at ~10 mK surround the array
30 cm of low activity lead will be used to shield from the dilution unit and from the environmental radioactivity
Neutron shielding: 18 cm thick polyethylene + 2 cm of H3BO3 powder
Alushta – 6 September 2011
Luca Gironi

21. CUORE CUORE crystals The production started at SICCAS Jiading in 2008
~ 30 crystals/month
~ 700 crystals already at LNGS
CUORE Crystal Validation Run – CCVR: a dedicated cryogenic setup to test crystals randomly chosen
7 CCVR already performed:
the bulk activity is within the limit specified in the contract with the crystals producer
improved the Cuoricino bolometric performance
FWHM on the internal alphas from 210Po (5407 keV) = 5.2 keV on average
lowered the energy thresholds thanks to a new trigger algorithm
- a better understanding of the background
- possibility to study Dark Matter spin independent interaction with CUORE
Alushta – 6 September 2011
Luca Gironi

22. CUORE schedule 2008: Hut construction Crystal production 2009–2010:
Engineering/design/fabrication
2011:
Clean room commissioning
CUORE-0
2012–2013:
CUORE detector assembly
CUORE cryogenics
CUORE electronics & DAQ
2014: Data taking!
CUORE hut
Crystal handling robot
Gluing tests
Tower garage
Bonding tests
Alushta – 6 September 2011
Luca Gironi

23. CUORE scientific goal
In 5 years of live time, with the foreseen aim of 0.01 c/keV/kg/y
CUORE has a 1σ sensitivity of
Alushta – 6 September 2011
Luca Gironi

24. Conclusions
0νDBD plays a primary role in the study of neutrino nature, in the study absolute neutrino mass scale and has a special relevance for testing the physics beyond the standard model
Te02 bolometers proved to be a competitive tool for the DBD search
Cuoricino has provided the most stringent limits on 0νDBD of 130Te and showed that an experiment like CUORE is feasible
CUORE-0 will be the first test of a CUORE-like tower from the assembly to data taking and a competitive experiment itself
CUORE data taking is foreseen for 2014
Alushta – 6 September 2011
Luca Gironi

25. Thank you for the attention!
Conclusions
Thank you for the attention!
Alushta – 6 September 2011
Luca Gironi

26. Fine

27. Backup slides

28. Nuclear Matrix Elements
130Te half-life limit (90% C.L.):
T0ν1/2>2.8 x 1024 y
Effective neutrino mass limit:
mββ < 300÷710 meV
NME bibliography:
J. Barea et al., Phys. Rev. C 79, (2009)
F. Simkovic et al., Phys. Rev. C 77, (2008)
O. Civitarese et al., J. Phys. Conf. Ser. 173, (2009)
J. Menendez et al., Nucl. Phys. A 818, 139 (2009)
Alushta – 6 September 2011
Luca Gironi

29. 0νDBD experiments: comparison
Sense and sensitivity of double beta decay experiments
J.J. Gomez-Cadenas et al.
Journal of Cosmology and Astroparticle Physics
June 2011
Alushta – 6 September 2011
Luca Gironi

30. 0νDBD experiments: comparison
Sense and sensitivity of double beta decay experiments
J.J. Gomez-Cadenas et al.
Journal of Cosmology and Astroparticle Physics
June 2011
Alushta – 6 September 2011
Luca Gironi

31. CUORE: Dark Matter
Alushta – 6 September 2011
Luca Gironi

32. CUORICINO coincidence analysis
__ single hit events
__ double hit events
238U and 232Th alpha peaks
due to crystal surface contaminations
Alushta – 6 September 2011
Luca Gironi

33. CUORE: the hut 2nd - electronics 1st - clean room
0th – cryostat equipment
Alushta – 6 September 2011
Luca Gironi

34. CUORE gluing station, garage and working plane
Crystal handling robot
Epoxy mixing/dispensi ng robot
Universal Working Plane
Tower garage
Bonding tests
Alushta – 6 September 2011
Luca Gironi

35. CUORE status: the cryostat
4 companies to pour, work, and form low-rad copper into 6 vessels (+ flanges)
First 3 vessels (300K, 40K, 4K) are in process of being electron-beam welded
Delivery scheduled for Sep 2011
More delicate inner 3 vessels will be manufactured next year
Alushta – 6 September 2011
Luca Gironi

36. Cuoricino cosmic background study
1.1 μ/hr/m2
10 plastic scintillators were arranged around cryostat during final 3 months of Cuoricino data taking
Searched for correlations between muon triggers and single-site events in bolometer array
Measured rate was consistent with zero in the νββ region of interest (R.O.I.), corresponding to an upper limit of:
Cuoricino background in R.O.I. is much higher:
Rμ < counts/keV/kg/y (95% C.L.)
E. Andreotti et al. (CUORICINO Collaboration), Astropart.Phys.34:18-24 (2010) [arXiv:nucl-ex/ ].
RCuoricino ~ 0.2 counts/keV/kg/y
Alushta – 6 September 2011
Luca Gironi

37. Pulse shape and anticoincidence cuts
Alushta – 6 September 2011
Luca Gironi

38. Cuoricino analysis sequence
Pulse amplitude evaluation
Pulse amplitude is the paramount observable, because it’s proportional to the amount of energy deposited
Raw pulse is processed using so-called Optimum Filter (OF)
Gain stabilization
Bolometer gain is temperature-dependent, so...
Detector response varies with natural temperature drift
Gain is “stabilized” by plotting heater pulse amplitude vs. baseline and fitting a line to the points
Energy calibration
Need to convert the stabilized pulse amplitudes to energy
Thorium sources were lowered next to detector ~ once/month
Global and pulse shape cuts
Used to reject nonphysical events (e.g., electronic noise) and pileup events
Anticoincidence cuts
0νββ decay should produce a “single- site” signal 85% of the time
Excluding multi-site events (±50 ms) reduces background by ~ 15% in the region of interest while retaining more than 99% of signal
Energy spectrum fit
Alushta – 6 September 2011
Luca Gironi

39. What is the most favorable isotope and the best technique ?
Phase space factor: 48Ca, 150Nd, 96Zr
Nuclear matrix element  not yet reliable predictions
Backgrounds > 2,6 MeV Ca, 150Nd, 96Zr, 100Mo, 82Se, 116Cd
> 3.2 MeV (radon) 48Ca, 150Nd, 96Zr
Enrichment: 130Te (Natural isotopic abundance 34%)
136Xe (gaz, easy to enrich)
Best techniques :
Bolometers, Ge diodes: energy resolution 130Te (82Se, 116Cd), 76Ge
Tracko-calo : background rejection 82Se, (48Ca, 150Nd)
TPC Xe: background rejection if tagging of Ba 136Xe
Large liquid scintillator: mass of isotopes 136Xe, 150Nd
Alushta – 6 September 2011
Luca Gironi

40. Ge diode detectors Heidelberg-Moscow (2001) IGEX (2002)
~11 kg of enriched 76Ge (86%)
IGEX (2002)
~ 8.4 kg of enriched 76Ge (86%)
8.9 kg.yr without PSA
4.6 kg.y with PSA
0.06 cts/keV/kg/yr
T 1/2 > yr (90% CL)
T 1/2 > yr (90% CL)
<mn> < eV (90% CL)
<mn> < eV (90% CL)
Eur. Phys. J., A 12 (2001) 147
Phys. Rev. D65 (2002)
Alushta – 6 September 2011
Luca Gironi

41. Tracko-calo detector NEMO3 bb events Bckg: 0.025 cts/keV/kg/yr e- e-
Drift chamber (6000 cells)
Plastic scintillator + PMT (2000)
10 kg of isotopes
DE/E (FWHM) : 8 3 MeV
Located in Modane Underground Lab (France)
Bckg: cts/keV/kg/yr
bb events
82Se (0,93 kg)
Multi-source detector E1 e-
Vertex e-
E1+E2= 2088 keV
t= 0.22 ns
(vertex) = 2.1 mm E2
Alushta – 6 September 2011
Luca Gironi

42. SuperNEMO 1 m 5 m Top view 20 modules for 100 kg
Source (40 mg/cm2) 12m2
Tracking (~ Geiger cells).
Calorimeter (500 channels)
Total:~ – geiger cells channels
~ PMT
5 m
1 m
Top view
Alushta – 6 September 2011
Luca Gironi 42

43. SuperNEMO DE/E < 4% (FWHM) @ Qbb demonstrated
(< 1 MeV)
Commissioning of wiring robot
FWHM = 7,1 %
(7,6% before energy
loss correction)
SuperNEMO phase I : – 2014
Contruction demontrator module with 7 kg of 82Se
2013
Sensitivity in 1 year: T1/2 < y <mn> < 0.2 – 0.6 eV
SuperNEMO phase II : – 2019
100 kg of 82Se (or 150Nd,or 48Ca)
T1/2 > 1026 y <mn> < 0.05 – 0.14 eV
LSM extension
Alushta – 6 September 2011
Luca Gironi

44. GERDA Removal of matter
Use of liquid nitrogen or argon for active shielding
Segmented detectors in futur
Improvement of Pulse Shape Analysis
PHASE I: 17.9 kg of enriched 76Ge (from HM and IGEX)
In 1 year of data if B=10-2 cts/keV/kg/yr (check of Klapdor’s claim)
Start 2011 at Gran Sasso T1/2 > yr <mn> < 0.25 eV>
PHASE II: 40 kg of enriched 76Ge (20 kg segmented) 2012
if B=10-3 cts/keV/kg/an T1/2 > yr in 3 years of data <mn> <0.1 eV>
Alushta – 6 September 2011
Luca Gironi

45. GERDA Nov/Dec.’09: Liquid argon fill
Jan ’10: Commissioning of cryogenic system
Apr/Mai ’10: emergency drainage tests of water tank
Apr/Mai ’10: Installation c-lock
May ’10: 1st deployment of FE&detector mock-up
June ‘10: Commissioning with natGe detector string
Soon: …….
Alushta – 6 September 2011
Luca Gironi

46. Majorana Ge diodes R&D phase 30-60 kg of 86% enriched 76Ge crystals
Very pure material
(Electroformed copper)
Segmentation
PSD improvement
R&D phase kg of 86% enriched 76Ge crystals
Some of the crystals segmented
Bckg goal ~ 1 count/ROI/t-yr (after analysis cuts)
30 kg of enriched Ge, running 3 yr. Data taking scheduled for 2011
T1/2 > yr <mn> < eV (could confirm or refute Klapdor’s claim)
Collaboration with Gerda for 1 ton detector
Alushta – 6 September 2011
Luca Gironi

47. Liquid Xe TPC EXO-200 Ionization + scintillation
DE/E (FWHM)= 3.3
Possibility of Baryum ion tagging by
Laser florescence (136Xe  136Ba e
200 kg of 136Xe, no Ba ion tagging
Installation in WIPP underground lab
Possibility to measure bb(2n)
EXO-200 full of natural Xe - Tuning on all systems - Engineering runs - Physics mode as soon as possible
Alushta – 6 September 2011
Luca Gironi

48. EXO-200 http://arxiv.org/abs/1108.4193v1 Alushta – 6 September 2011
Luca Gironi

49. Scintillator loaded with Nd
SNO++
Scintillator loaded with Nd
500 kg of 150Nd
1 year
<mn> = 150 meV
Test of light attenuation
Study of Nd purification (factor 1000
per pass in Th and Ra)
56 kg of 150Nd (0,1 % of natural Nd) yr of data <mn> ~0.08 eV
500 kg of 150Nd 4yr <mn> ~ 0.03 eV
Alushta – 6 September 2011
Luca Gironi
F. Piquemal (CENBG) LP07

50. KamLAND-Zen
Alushta – 6 September 2011
Luca Gironi

51. CANDLES Pure CaF2 crystals CANDLES III
Wave length shifter in LS
PSD to reject g and a
CaF2(Pure)
Liquid Scintillator
(Veto Counter)
Buffer Oil
Large PMT
CANDLES III
103 cm3 × 96 crystals  305 kg
Data taking in Kamioka
Expected BG: 0.14 event/yr (30 µBq/kg)
<mn> ~0.5 eV
CANDLES IV : 3 tons of CaF2 (3 mBq/kg) 6 yr <mn> ~0.1 eV
Alushta – 6 September 2011
Luca Gironi

52. COBRA Array of 1cm3 CdZnTe detectors
Cd-113 beta decay with half-life of about 1016 yrs
4x4x4 detector array = 0.42 kg CdZnTe
Installed at LNGS
Test of coincidence rejection
Measure of 113Cd
Alushta – 6 September 2011
Luca Gironi
F. Piquemal (CENBG) LP07