CUORE - Agenda (Indico)CUORE projected sensitivity (5 years, 90% C.L.): T1/2 > 9 × 1025 yr Primary...

CUOREOliviero Cremonesi INFN - Sez. Milano Bicocca

CUORE October 2, 2017 - Meeting of the LNGS Scientific Committee

Oliviero Cremonesi - October 2, 2017 - Meeting of the LNGS Scientific Committee

CUORE

2

Outline

• Status

• First results

• Plans


CUORE

3

CUORE(Cryogenic Underground Observatory for Rare Events)

Closely packed array of 988 TeO2 crystals arranged in 19 towers

130Te: • large transition energy: Qββ (130Te) 2527.5 keV • highest natural isotopic abundance (33.8%)

CUORE projected sensitivity (5 years, 90% C.L.):T1/2 > 9 × 1025 yr

Primary goal: search for 0νββ decay in 130Te

CUORE design parameters: • mass of TeO2: 742 kg (206 kg of 130Te ) • low background aim: 10-2 c/(keV⋅kg⋅yr)• energy resolution: 5 keV FWHM in the Region Of Interest (ROI) • high granularity • deep underground location • strict radio-purity controls on materials and assembly


CUORE

4

The CUORE cryostat

DetectorTowers

Top LeadShield

Side LeadShield

300 K

40 K

4 K

600 mK50 mK

10 mK

Bo�om LeadShield

Plates:• Designed to cool down ~1 ton detector to ~10 mK • Mechanically decoupled for extremely low vibrations • Low background environment

• Cryogen-free cryostat • Fast Cooling System (4He gas) down to ~50K • 5 pulse tubes cryocooler down to ~4K • Dilution refrigerator down to operating temperature ~10 mK • Nominal cooling power: 3 μW @ 10mK • Cryostat total mass ~30 tons • Mass to be cooled < 4K: ~15 tons • Mass to be cooled < 50 mK: ~3 tons (Pb, Cu and TeO2)


CUORE

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The CUORE Collaboration


CUORE

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CUORE construction• June 2016: last steps of the CUORE construction process

• Installation of the front-end electronics (2nd floor) • Installation of the DAQ (2nd floor) • Detector installation preparation

• August 2016: detector installation

• Installation of cryostat interfaces • Test of readout wires • Close-out of the cryostat vessels • IVC eventually closed in October 2016

• September-November 2016:

• December 5, 2016: cool-down start

• December 2, 2016: system close-out complete


CUORE

7

CUORE cooldown• Reached a stable base temperature of ~7

mK on Jan 27, 2017

• Cooldown to base T: ~ 3 days

• Lowest temperature reached: 6.7 mK

• 984/988 working detectors

• Excellent performance @ full load�t [d]

0 0.5 1 1.5 2 2.5 3 3.5 4

T[K

]

0.01

0.1

1

10

Still plate

HEX plate

MC plate

CUORE cool down

Start: 2017-01-23 10:00

• Stable operation

14.0

14.2

14.4

14.6

14.8

15.0

15.2

15.4

15.6

15.8

16.0

12/5/17 14/5/17 16/5/17 18/5/17 20/5/17 22/5/17

Mixing Chamber Temperature

Base

tem

pera

ture

[mK]

6

8

10

12

14

16

18

20

0 5 10 15Power on mixing chamber [µW]

HEXisconnectedtotoplead

dilu1onstarts


CUORE

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Pre-operationAfter the successful cool-down, we faced with the challenge of operating a thousand bolometers in a completely new system

A long list of activities • DAQ and front-end electronics optimization • Detector working points

• Select representative subset • Load curves • Temperature scan for the best operating conditions

• Noise reduction • vibration induced • electrically induced

End of March 2017: • optimization not yet complete • decision to start calibrations and science runs • selected working temperature: 15 mK


CUORE

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Transition to operationDetector Performance

• The key parameters expected from CUORE are: • energy resolution• backgrounds in ROI

• Prioritary to obtain informations on both• CUORE has opted for a gradual transition to operation, alternating science runs to technical

measurements aiming to achieve better performance and to demonstrate improvements towards the ultimate performance.

First Physics Result• With few weeks of data CUORE can report the world’s best limit on 0νββ from 130Te with a high

degree of confidence. • A preliminary physics result can demonstrate the successful operation of CUORE and be worth publishing

by itself.• Milestones:

• Preliminary results for TAUP 2017 • First CUORE physics paper by October 2017


CUORE

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Schedule for Early Physics with CUORE

2017:Feb-Mar: system optimisationApr-May: science runsJun-Jul: system optimisationAug-Sep: science runsOct-Nov: system optimisation

2018:Science runs

Firstresults:Apr-May2017(ds3018)


CUORE

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Science runs• Science operations started on April 14, 2017

• Dataset 1: very short (identified issue with the thermistor bias on about 1/3 of the channels)

• Reoptimization of the detector working point • Dataset 2: 3 weeks of physics data bracketed by

2 calibration periods (May 4 - June 11) • Second optimization campaign • Dataset 3: August - September 2017

Operational performance: • 984/988 operational channels• Excellent data-taking efficiency when in operations • Much improved detector stability, compared to

Cuoricino/CUORE-0 • Calibrations/physics ratio data still to be optimized to

maximize 0νββ sensitivity

65.4%

21.8%

9.4%3.3%

Physics CalibrationOther Test

May

June

2017

Acquired statistics for 0νDBD decay search: • natTeO2 exposure: 38.1 kg yr • 130Te exposure: 10.6 kg yr

Dataset 2 time breakdown


CUORE

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Calibration spectrum

• 232Th sources deployed inside the CUORE detector

• Energy spectrum of all the CUORE detectors

Energy [keV]500 1000 1500 2000 2500

Even

ts [c

ount

s / k

eV]

210

310

410

510Calibration spectrum

CUORE Preliminaryyr⋅Exposure: 38.1 kg


CUORE

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

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Detector performance: energy resolution• 899 (90%) best performing channels used for initial

analysis; most discarded channels had poor line or pulse shapes, and should be recovered in future runs

• Average (“harmonic mean”) energy resolution in calibration runs: 10.6 keV FWHM @ 2615 keV

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

• Significantly better performance in physics data: (7.9 ± 0.6) keV FWHM @ 2615 keV

FWHM [keV]5 6 7 8 9 10 20 30 40 50 60 70

Chan

nels

0

20

40

60

80

100

120

Calibration resolution at 2615 keVCUORE Preliminary

yr⋅Exposure: 38.1 kg


CUORE

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Detector performance: line shape• Fit components:

• a flat background • a step-wise smeared background • a double gaussian for the main peak • a combination of gaussian escape lines

• A quadratic dependence of the energy resolution is determined from gamma lines in the physics spectrum

Energy [keV]2560 2580 2600 2620 2640 2660 2680

Even

ts [c

ount

s / 2

keV

]

1

10

210

310



Tower 9

Energy [keV]800 1000 1200 1400 1600 1800 2000 2200 2400 2600

Rela

tive

reso

lutio

n

0.5

0.55

0.6

0.65

0.7

0.75

0.8

Resolution relative to 2615 keV calibration line




CUORE

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Analysis steps

Essentially the same steps and procedures developed and used for CUORE-0 (Phys. Rev. C 93, 045503 (2016) - arXiv:1601.01334)

• Acquisition of triggered signals • Data preprocessing: estimation of raw parameters • Pulse filtering • Thermal Gain Stabilization (TGS) • Energy calibration • Particle event selection • Coincidence analysis • Energy spectrum


CUORE

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Background spectrum: γ regionDataset 2

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


Energy [keV]2350 2400 2450 2500 2550 2600 2650 2700

Phys

ics e

vent

rate

[cou

nts /

(keV

kg

yr)]

3−10

2−10

1−10

1 CalibrationPhysics



CUORE

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Blinded spectrum• To blind our data we 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.

• This method of blinding the data preserves the integrity of the possible 0νDBD events while maintaining the spectral characteristics with measured energy resolution and introducing no discontinuities in the spectrum.

Energy [keV]2400 2450 2500 2550 2600 2650 2700

Eve

nts [

coun

ts / k

eV]

02468

1012141618

Tl208

Bi214 Co60


CUORE physics spectrum (blinded)

Energy [keV]2400 2450 2500 2550 2600 2650 2700

Eve

nts [

coun

ts / k

eV]

02468

1012141618 Tl208

Bi214 Co60


CUORE physics spectrum (unblinded)

Energy [keV]2400 2450 2500 2550 2600 2650 2700

Eve

nts [

coun

ts / k

eV]

02468

1012141618 Blinded

UnblindedTl208

Bi214 Co60


• When all data analysis procedures are fixed the data are eventually unblinded

• The blinding procedure is more evident by comparing directly the two spectra

Qββ


CUORE

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Fit in the ROI• We determined the yield of 0νββ events by performing a simultaneous UEML fit in the energy region

2465-2575 keV • 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

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 kgQββUnblinded spectrum fit


CUORE

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Fit in the ROI

We have also evaluated limits according to “W. Rolke et al., Nucl. Instrum. Meth. A 551, 493-503 (2005)”: - Half-life limit (90% CL, including systematics): 6.1×1024 yr - Decay rate limit (90% CL, including systematics): 0.11×10-24 / yr - Median expected sensitivity: 3.7×1024 yr

• Best fit decay rate: (-0.03–0.04+0.07 (stat.) ± 0.01 (syst.))×10-24 / yr• Decay rate limit (90% CL, including systematics): 0.15×10-24 yr-1

• Half-life limit (90% CL, including systematics): 4.5×1024 yr• Median expected sensitivity: 3.6×1024 yr (arXiv:1705.10816)

• Profile likelihood • Integrated on the physical region

- Region of interest: 2465 to 2575 keV- ROI background index: (9.8–1.5+1.7) × 10-3 c/(keV⋅kg⋅yr)- Events in the region of interest: 50- Best fit for 60Co mean: (2504.8 ± 1.2) keV

Trigger and energy reconstruction (98.469 ± 0.009) %Anti-coincidence (99.3 ± 0.3) %Pulse shape analysis (64 ± 3) %All cuts except containment (62.6 ± 3.4) %0vββ containment (88.345 ± 0.085) %Total 0vββ efficiency (55.3 ± 3)%

Efficiencies


CUORE

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


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Combination with previous results

• We combined the CUORE result with the existing 130Te

• 19.75 kg·yr of Cuoricino • 9.8 kg·yr of CUORE-0

• The combined 90% C.L. limit is T0ν > 6.6 × 1024 yr

Combined “Rolke” limit: 8.1×1024 yr [meV]lightestm

1−10 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

NME: Phys. Rev. C 91, 034304 (2015) Phys. Rev. C 87, 045501 (2013) Phys. Rev. C 91, 024613 (2015) Nucl. Phys. A 818, 139 (2009) Phys. Rev. Lett. 105, 252503 (2010)

Experiments: 130Te: 6.5 × 1024 yr from this analysis 76Ge: 5.3 × 1025 yr from Nature 544, 47–52 (2017) 136Xe: 1.1 × 1026 yr from Phys. Rev. Lett. 117, 082503 (2016) 100Mo: 1.1 × 1024 yr from Phys. Rev. D 89, 111101 (2014) CUORE sensitivity: 9.0 × 1025 yr

mββ < 210–590 meV

Addi1onalphysicsrun:Aug2017(ds3020)


CUORE

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Science runs• Total statistics doubled with respect to June 2017

• All the available data have been fully reprocessed • Adopted the usual blinding procedure • Data analysis almost complete • Expected release of results: Oct. 23,2017

• In the meantime ….


CUORE

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System optimization• Further optimization steps:

• Detector commissioning stopped in April to start science runs • Still room for improvements • Mainly directed to: detector performance and noise abatement

• Detector optimization campaigns: June-July and fall 2017 • Careful investigation/upgrades to the electronics grounding in

the CUORE Faraday cage • Active cancellation of the PT-induced noise • Optimization of the operating temperature and detector

working points • System upgrades • Software and analysis upgrades

just started


CUORE

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Conclusions• The cryostat is working extraordinarily well. • With 3 weeks of physics data we have accumulated higher exposure than CUORE-0/

Cuoricino and surpassed their limit. • Total exposure: 38.1 kg⋅y • Invaluable operational experience • Important information on detector performance, noise, resolutions, background levels

• Developed and debugged physics tools, stress-tested end-to-end data processing with quality appropriate for science results

• Background rates are consistent with the background model • New data taken during the summer (still embargoed) • Available data have been fully reprocessed

• Further improvements possible: • Detector optimization campaigns have been

scheduled, focused on improving the resolution through noise reduction.

• First results already available • More to come

CUORE - Agenda (Indico)CUORE projected sensitivity (5 years, 90% C.L.): T1/2 > 9 × 1025 yr Primary...

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