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CUORE
I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Performance of the CUORE bolometers
- First CUORE results -
I.NutiniGran Sasso Science Institute
INFN Laboratori Nazionali del Gran Sasso on behalf of the CUORE collaboration
103° Congresso Nazionale della Società Italiana di FisicaTrento - Povo, 11-15 settembre 2017
1
CUORE
2I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE - Cryogenic Underground Observatory for Rare Events Primary goal: Search for neutrino-less double beta (0νββ) decay of 130Te
The CUORE experiment and the 0vββ search
Why 130Te:• Large transition energy:
Qββ (130Te) = 2527.5 keV • Highest natural isotopic abundance
(η = 33.8%) • 130Te within the detector absorber of TeO2
(high detection efficiency ε) • Reproducible growth of large number of
high quality crystals (M)
S
0⌫(n�) = ln2 ✏
1
n�
x ⌘ NA
MA
rM T
B �
Experimental 0vββ detection sensitivity:
- Lepton number violation process (BSM) - Majorana nature of neutrino - Constraints on neutrino mass hierarchy and scale - Not yet observed T0v > 1024-25 yr
DetectorTowers
Top LeadShieldSide LeadShield
300 K
40 K
4 K
StillHeat Exchanger
Mixing Chamber
Bottom LeadShield
Plates :
CUORE
3I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
The CUORE experiment and the 0vββ search
• Closely packed array of 988 TeO2 crystals (19 towers of 52 crystals 5×5×5 cm3, 0.75 kg each) High Mass of TeO2: 742 kg (206 kg of 130Te ) and high granularity
• Low background: - Deep underground location (Gran Sasso National Labs - LNGS), - Strict radio-purity controls on materials
and assembly, - Passive shields (Pb) from external and cryostat radioactivity Background aim: 10-2 c/(keV⋅kg⋅yr)
• Low vibrations - Multistage cryogen-free cryostat: - Mass to be cooled down: ~15 tonnes (Pb, Cu and TeO2) - TeO2 detectors operating temperature: ~10 mK Energy resolution aim: 5 keV FWHM in the Region Of Interest (ROI)
CUORE S0v sensitivity in 5 years (90% C.L.): ~ 9 x 1025 yr
The CUORE challenge:
CUORE
4I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE TeO2 bolometers
CUORE module: a tower
CUORE 19 towers array52 (nat)TeO2 crystals Absorber = 0vββ source
1 Ge NTD thermistor for each crystal
1 Si heater for each crystal <— Cu frames and PFTE holders Cu-PEN cables —>
CUORE
5I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE cooldown and data-takingCryogenic infrastructure and auxiliary systems
Detector Calibration System12 232Th γ-ray sources (thoriated tungsten) are cooled to base temperature and lowered into the experimental volume for calibration
Shieldings- External lead shielding and concrete support structure - Internal Ancient Roman Lead Shield (6 cm thick, 5 tons) @ 4K - Internal Top Lead Shield (30 cm thick, 2.5 tons) @ 50 mK
Multistage cryogen-free cryostat: - Fast Cooling System- 5 Pulse Tube cryocoolers (down to 4 K) - Continuous-cycle 3He/4He dilution refrigerator (down to base temperature ~10 mK)
35 K
4 K
Still 800 mK
Heat exchanger 50 mK
Mixing chamber10 mK
Roman lead shield @4 K
CUORE
6I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE cooldown and data-taking
27.01.2017 the first CUORE pulse!
- Cryogenic system commissioning : completed in Feb.2016 - Detector assembly and installation: completed at the end of Aug. 2016 - Detector cooldown: Started at the beginning of Dec. 2016, Cooldown time: ~ 20 days down to ~3.4 K, vacuum pumping into the inner volume, ~ 1.5 days down to ~ 10 mK
Observed first detector pulses just after the cool down without any optimization
CUORE
7I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDetector pre-operations and optimization phase (January-March 2017):
Noise optimization: • Electronics noise attenuation • Vibrations reduction (detector must be mechanically isolated) • Pulse tube relative phase shift tuning
Temperature scan: Temperature scan around base temperature to choose the one that optimizes the signal and at the same time allows to work with the designed NTD resistance. Selected working temperature: 15 mK
Setting the working points: Load curves scan to choose the best bias voltage to feed each channel’s NTD: • linear behavior for small temperature variations • maximization of signal to noise ratio • optimization of pulse amplitude
CUORE
9I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results
Science operations started on April 14, 2017 • First short dataset: test data processing tools and
re-optimization of the detector working points • Second dataset: 3 weeks of physics data
bracketed by an initial and a final calibration (May 4 - June 11) —> First CUORE physics results
• Second optimization campaign and new dataset - physics runs - ongoing from August
CUORE science runs (from April 2017)
Operational performance- 984/988 operational channels - Excellent data-taking efficiency - Improved detector stability - 899/984 best performing channels used for initial analysis
Acquired statistic for 0νββ decay search
natTeO2 exposure: 38.1 kg yr
130Te exposure: 10.6 kg yr
May
June
2017Second Dataset - Time breakdown
65.4 %
21.8 %
9.4 %3.3 %
Physics CalibrationOther Test
CUORE Preliminaryyr⋅Exposure: 38.1 kg
CUORE Preliminaryyr⋅Exposure: 38.1 kg
Run Time Breakdown
Energy [keV]500 1000 1500 2000 2500
Phys
ics e
vent
rate
[cou
nts /
(keV
kg
yr)]
3−10
2−10
1−10
1
10
CalibrationPhysics
CUORE Preliminaryyr⋅Exposure: 38.1 kg
CUORE
10I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results
Calibration and Background spectra
Calibration: 232Th sources deployed inside the CUORE detector Background - Physics: Spectrum is consistent with the background expectations
Cumulative energy spectrum from all the channels selected for the 0vββ initial analysis
Energy [keV]2560 2580 2600 2620 2640 2660 2680
Even
ts [c
ount
s / 0
.5 k
eV]
0
2000
4000
6000
8000
10000
12000 CUORE Preliminaryyr⋅Exposure: 38.1 kg
Energy [keV]2570 2580 2590 2600 2610 2620 2630 2640 2650 2660
]σ
Resid
ual [
2−1−0123
Energy [keV]2570 2580 2590 2600 2610 2620 2630 2640 2650 2660
Even
ts [c
ount
s / 2
keV
]
05
10152025303540 CUORE Preliminary
yr⋅Exposure: 38.1 kg
CUORE
11I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results
Calibration and Background spectra
• Average (“harmonic mean”) energy resolution in calibration runs: 10.6 keV FWHM @ 2615 keV
• Significantly better performance in physics data (7.9 ± 0.6) keV FWHM @ 2615 keV
Detector performance - Energy resolution @208Tl decay gamma-peak:
Energy [keV]2480 2500 2520 2540 2560
]σ
Resid
ual [
2−1−0123
Energy [keV]2480 2500 2520 2540 2560
Even
ts [c
ount
s / 2
.5 k
eV]
0123456789 CUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kg
CUORE
12I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results0νββ analysis
Energy [keV]2400 2450 2500 2550 2600 2650 2700
Eve
nts [
coun
ts / k
eV]
02468
1012141618 Blinded
UnblindedTl208
Bi214 Co60
CUORE Preliminaryyr⋅Exposure: 38.1 kg
Fit to evaluate best fit decay rate for 130Te: Simultaneous unbinned extended maximum likelihood fit - ROI region: [2465,2575 keV] around Qββ (130Te). - Events selection efficiency: (62.6 ± 3.4)% - ROI background index:
(9.8–1.5+1.7) × 10-3 c/(keV⋅kg⋅yr)
Considering the overall 0νββ signal efficiency: (55.3 ± 3.0)% - Best fit decay rate: (-0.03–0.04+0.07(stat.) ± 0.01 (syst.)) × 10-24/yr
Half-life limit (90%C.L including syst.): T0ν (130Te) > 4.5 x 1024 yr
CUORE
13I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results
Combined fit: CUORE + CUORE-0 + Cuoricino
Exposure 130Te: 19.75 kg·yr Cuoricino, 9.8 kg·yr CUORE-0, 10.6 kg yr CUORE
Bayesian half-life limit (90% CL) T0ν (130Te) > 6.6 × 1024 yr
Limit on mββ: mββ < 210 - 590 meV
[meV]lightestm1−10 1 10 210
[meV
]ββ
m
1−10
1
10
210
310
(Preliminary)Cuoricino + CUORE-0 + CUORE limit (Te)
CUORE sensitivity (Te)
Normal hierarchy
Inverted hierarchy
0 0.2 0.4 0.6 0.8 1
1−10
1
10
210
310
Other isotopes
Mo
Ge
Xe
0νββ analysis
1
T 0⌫1/2
/ G(Q�� , Z)|Mnucl|2|m�� |2Effective neutrino mass term
CUORE
14I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Conclusions
CUORE is the first tonne-scale bolometric 0νββ detector. First months of CUORE operations: • First CUORE physics results of T0ν in 130Te after 3 weeks of data taking • Exceptional cryostat performance and important information on
detectors characterization, noise, resolutions and background levels. • Detector optimization campaign focused on improving the resolution
through further noise reduction • Data taking has restarted at the end of July 2017, physics runs
ongoing • More to come!
CUORE
15I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Thank you on behalf of The CUORE collaboration
CUORE
16I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Backup
CUORE
17I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
The CUORE experiment and the 0vββ search
Double beta decay is a very rare nuclear decay (N,Z) → (N-2, Z+2)
2vββ: - 2nd order process allowed in SM - Observed in several nuclei: !~1019-21 y 0vββ: - Lepton number violation process (BSM) - Majorana nature of neutrino - Constraints on neutrino mass hierarchy and scale - Not yet observed !>1024-25 y 2vββ
0vββ 1
T 0⌫1/2
/ G(Q�� , Z)|Mnucl|2|m�� |2
Phase space integral Nuclear matrix elementEffective neutrino mass termm�� = |⌃im⌫iU
2ei|
Q�� Q-value of the ββ decay
CUORE
18I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE TeO2 bolometersBolometer principle of operation
Heat bath ~ 10 mK
(copper)
Thermal coupling
(PTFE)
Thermistor
(NTD-Ge)
Absorber Crystal
(TeO2)
Absorber crystal (nat)TeO2 : 0vββ source
C(T) ~ 2 x 10-9 J/K (@ 10 mK) Thermistor NTD-Ge
Rwp ~ 10-100 MΩ
∆T
⌧
R(T ) = R0exp(T0T )1/2
C(T ) / T 3 Lattice specific heat
�T / Edep
C⇡ 100µK
MeV
Simplest thermal model: One thermal capacity (crystal)One thermal link G (btw crystal/heat bath)
Amplitude of the pulse ∝ Energy deposit
⌧ =G
C⇡ 1s
CUORE
19I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE cooldown and data-takingCryogenic infrastructure and auxiliary systemsMultistage cryogen-free cryostat: - Fast Cooling System- 5 Pulse Tube cryocoolers (down to 4 K) - Continuous-cycle 3He/4He dilution refrigerator (down to base temperature ~10 mK)
35 K
4 K
Still 800 mK
Heat exchanger 50 mK
Mixing chamber10 mK
FCSPT
CUORE
20I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
CUORE cooldown and data-takingCryogenic infrastructure and auxiliary systems
Cryostat support structure
CUORE
21I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDataset 2: Calibration spectrum - Line shape
Calibration: 232Th sources deployed inside the CUORE detector
Energy [keV]2560 2580 2600 2620 2640 2660 2680
Even
ts [c
ount
s / 2
keV
]
1
10
210
310
CUORE Preliminaryyr⋅Exposure: 38.1 kg
CUORE Preliminaryyr⋅Exposure: 38.1 kg
Tower 4 Fit components: • a flat background • a step-wise smeared background • a double gaussian for the main
peak • a combination of gaussian
escape lines
Fit on a tower by tower basis
Energy [keV]500 1000 1500 2000 2500
Even
t rat
e [c
ount
s / (k
eV k
g yr
)]
3−10
2−10
1−10
1
10
CUORE-0CUORE
Ac228 Co60Co60
K40
Bi214
Tl208
Bi214
Bi214
Tl208
CUORE Preliminaryyr⋅Exposure: 38.1 kg
CUORE
22I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDataset 2: Background spectrum
Background - Physics: Significant reduction in the γ region with respect to CUORE-0 (CUORE-like tower experiment), Spectrum is consistent with the background expectations
CUORE
23I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDataset 2: Background spectrum - Blinding
Blinding procedure: • Randomly move a fraction of events from
+/- 20 keV of 2615 keV to the Q-value and vice versa
• The blinding algorithm produces an artificial peak around the 0νDBD Q- value and blinds the real 0νDBD rate of 130Te.
• When all data analysis procedures are fixed the data are eventually unblinded Energy [keV]
2400 2450 2500 2550 2600 2650 2700
Eve
nts [
coun
ts / k
eV]
02468
1012141618 Blinded
UnblindedTl208
Bi214 Co60
CUORE Preliminaryyr⋅Exposure: 38.1 kg
Energy [keV]2480 2500 2520 2540 2560
]σ
Resid
ual [
2−1−0123
Energy [keV]2480 2500 2520 2540 2560
Even
ts [c
ount
s / 2
.5 k
eV]
0123456789 CUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kgCUORE Preliminary
yr⋅Exposure: 38.1 kg
CUORE
24I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDataset 2 : 0νββ analysis
Energy [keV]2400 2450 2500 2550 2600 2650 2700
Eve
nts [
coun
ts / k
eV]
02468
1012141618 Blinded
UnblindedTl208
Bi214 Co60
CUORE Preliminaryyr⋅Exposure: 38.1 kg
ROI Fit to evaluate best fit decay rate for 130Te: Simultaneous unbinned extended maximum likelihood fit ROI region: [2465,2575 keV] around Qββ (130Te). The fit has 3 components: • a posited peak at the Q-value of 130Te • a floating peak to account for the 60Co sum gamma line (2505 keV)• a constant continuum background, attributed to multi scatter Compton events from 208Tl and surface alpha events
- Overall signal efficiency: (55.3 ± 3.0)% - ROI background index: (9.8–1.5+1.7) × 10-3 c/(keV⋅kg⋅yr) - Half-life limit (90%C.L including syst.): T0ν (130Te) > 4.5 x 1024 yr
]-1 yr-24Decay rate [100.1− 0 0.1 0.2 0.3 0.4 0.5 0.6
NLL
02468
101214161820
CuoricinoCUORE-0CUORECUORE + CUORE-0 + Cuoricino
CUORE Preliminaryyr⋅Exposure: 38.1 kg
]-1 yr-24Decay rate [100.1− 0 0.1 0.2 0.3 0.4 0.5 0.6
NLL
0
2
4
6
8
10
12
14 CUORE (stat. only)
CUORE (stat. + syst.)
CUORE Preliminaryyr⋅Exposure: 38.1 kg
CUORE
25I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics resultsDataset 2: Background spectrum - NLL FITBest fit decay rate (-0.03–0.04+0.07 (stat.) ± 0.01 (syst.)) × 10-24 / yr
Bayesian Half-life limit (90%C.L including syst.): T0ν > 4.5 x 1024 yr
Median expected sensitivity based on actual exposure: S0ν > 3.6 × 1024 yr (with sensitivity paper technique) S0ν >3.3 × 1024 yr (with same fit technique as ROI fit)
Combined fit: CUORE + CUORE-0 + Cuoricino Bayesian half-life limit (90% CL) T0ν > 6.6 × 1024 yr
CUORE
26I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
Detector characterization and first physics results
CUORE GOAL: 0.01 counts/keV/kg/y
CL limit 90% Value
counts/keV/kg/yr
LNGS flux
Material screening
Measured in CUORE-0
Preliminary
CUORE background budget
CUORE
27I.Nutini, GSSI - INFN LNGS; 103° Congresso SIF, 15 Set. 2017
The CUORE collaboration
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