First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE...

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

Transcript of First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE...

Page 1: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

First neutrinoless double beta decay results from CUORE-0

L. Gironi on behalf of the CUORE collaboration

Università degli Studi di Milano - BicoccaINFN di Milano - Bicocca

10th  M E D E X '15  meetingPrague, June 09th - 12th, 2015 

Page 2: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

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

- Possibility to choose among all the ββ isotope

- Q-value in low background region

- Very low background level already reached but

surface contaminations

Bolometers for 0νDBD

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Why bolometers are suitable detectors for 0νDBD ?

TNT 0

TMaT 00B

0 BTM

0 BTM

BTM

TMaTB

0

abundance isotopic

efficiency detector

[keV] resolution energyy][c/keV/kg/ background B

[kg] mass detector

[y] time live

a

M

T

TMa

Page 3: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

TeO2 Bolometric DetectorsAt 10 mK, energy deposited in TeO2 results in a measurable change in temperature

Energy release → ΔT→ ΔR in the thermistor → ΔV

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

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ΔTtherm~ 10-20 μK/MeVΔTcryst ~ 0.1 mK/MeV

ΔRtherm ~ 3 MΩ/MeVΔVtherm ~ 0.3 mV/MeV

Page 4: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

The CUORE program

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Cuoricino2003-2008

M· T (130Te) = 19.75 kg.yr B = 0.169 ± 0.006

c/keV/kg/y∆ = 6.3 ± 2.5 keV FWHM

T1/2 > 2.8· 1024 y (90% C.L.)

B

TMTB

0

CUORE2015-2020

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.)

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)

Page 5: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

Cuoricino

mββ < (270-650) meV

(R)QRPA - Phys.Rev. C 77 045503 (2008)pnQRPA - JoP Conference series 173 012012 (2009)ISM - Nucl. Phys. A 818 139 (2009)IBM-2 - Phys.Rev. C 79 044301 (2009)

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62 TeO2 crystals (40.7 kg) operated at Gran Sasso (2003-2008)

• M· T (130Te): 19.75 kg.yr• ∆: 6.3 ± 2.5 keV FWHM• B: 0.169 ± 0.006 c/keV/kg/yr

T1/2 > 2.8 x 1024 y (90% C.L.)

0νββ upper limit

Page 6: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

Qββ

Cuoricino – Background

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α

α

Main sources of background in the ROI:

β/γ events α eventsQββ

30% Compton from 208Tl decays in cryostat60% Degraded alphas on copper surfaces10% Degraded alphas on crystal surfaces

Physics dataCalibration data

Page 7: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0

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

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Page 8: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE/CUORE-0 – Assembly line

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Clean Room for Detector Assembly and Storage

CUORE hutCuoricino/

CUORE-0 hut

CUORE-0 construction was carried out inside N2-flushed glove boxes in CUORE hut’s clean room.

Page 9: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 9

CUORE/CUORE-0 – Assembly lineSemi-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

Page 10: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 10

CUORE/CUORE-0 – Assembly lineTower 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

Page 11: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 11

CUORE/CUORE-0 – Assembly lineConnection to readout: Wire bonding

• All wire-bonding done in N2 flushed glove box

• Vertical bonding machine with auxiliary X-Y motion

Page 12: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0with 10mK shield

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CUORE/CUORE-0 – Assembly line

The successful operation of CUORE-0 demonstrated the validity of the CUORE tower assembly line and of the CUORE cleaning procedures.

CUOREtower

Tower storage

Page 13: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 13

CUORE-0

• Uses the old Cuoricino cryostat

• Electronics from Cuoricino

• Shielding from Cuoricino

• Cooled to base T (~10 mK) Mar 2013

Page 14: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0 – Data taking• M· T (130Te): 9.8 kg· yr of 130Te

• 51/52 NTDs online

• 50/52 heaters online

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Calibration data taking

Physics data taking

1st

cam

paig

n2

nd c

am

paig

n

Page 15: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 15

Total fit on the 2615 keV lineDistribution of energy resolution @ 2615

keV

CUORE-0 – Calibration energy resolution

The 5 keV CUORE goal has been

reached

CUORE-0Preliminary

CUORE-0Preliminary

Exposure-weightedHarmonic Mean

FWHM

RMS ofFWHM

Cuoricino 5.8 keV 2.1 keV

CUORE-0 4.9 keV 2.9 keV

Page 16: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0 – Background

• 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)

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Comparison of the total background spectrum in CUORE-0 and Cuoricino

2.7-3.9 MeV[c/keV/kg/y]

eff[%]

Cuoricino 0.110 ± 0.001 83 ± 1

CUORE-0 0.016 ± 0.001 81 ± 1

CUORE-0 Preliminary

Page 17: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0 – 0νDBD analysisData processing and analysis techniques are focused to the correct reconstruction of each eventenergy (optimal filtering technique) and eventually to the creation of the energy spectrum of the ROI:

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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)%

Page 18: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE-0 – 0νDBD searchAfter all cuts: 233 events in ROI [2470-2570 keV].

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Best value fit of the 0νDBD decay rate:

Г0ν= 0.01 ± 0.12(stat.) ± 0.01(syst.) x 10-24 yr-1

Background index in ROI:

0.058 ± 0.004(stat.) ± 0.002(syst.) c/keV/kg/y

We find no evidence for a signal and set 90% C.L. lower limit from profile likelihood:

yrT 241072 .01/2

Pro

file

neg

ati

ve log

-lik

elih

ood

CUORE-0 PreliminaryCUORE-0 Preliminary

Page 19: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 19

CUORICINO/CUORE-0 combined limitWe combine the CUORE-0 result with the existing 19.75 kg· yr of 130Te exposure from Cuoricino

yrT 241004 .01/2

This is the most stringent limit on this half-life !

Pro

file

negati

ve log-

likelih

ood

CUORE-0 Preliminary

Page 20: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015 20

Extrapolation to mββ

Combined half-life result as a limit on the effective Majorana neutrino mass:

mββ < (270-650) meV

IBM-2 Phys. Rev. C 91, 034304 (2015)QRPA-TU Phys. Rev. C 87, 045501 (2013)pnQRPA Phys. Rev. C 91, 024613 (2015)ISM Nucl. Phys. A 818, 139 (2009)EDF Phys. Rev. Lett. 105, 252503 (2010)

CUORE-0 Preliminary

Page 21: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

The CUORE program

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Cuoricino2003-2008

M· T (130Te): 19.75 kg.yr B = 0.169 ± 0.006

c/keV/kg/y∆ = 6.3 ± 2.5 keV FWHM

T1/2 > 2.8· 1024 y (90% C.L.)

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)

B

TMTB

0

CUORE2015-2020

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.)

Page 22: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE• 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 resolution @ ROI: 5keV

• background level: 0.01 c/keV/kg/y

• sensitivity (90% C.L., 5 years):

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yrT 251059 .01/2

Page 23: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE – Background mitigation efforts• Improve shielding and radio-purity of cryostat materials

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• 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

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)

Page 24: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE – Self shielding

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• CUORE-0: All bolometers face 10 mK shield

• CUORE: Only outermost crystals face 10 mK shield

Page 25: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

CUORE – Status

Assembly of the 19 CUORE towers is complete

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Expect to deploy the array in the cryostat later this year.

Page 26: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

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

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Plan to start operations by end of 2015.

Cryostat Vessel Flanges

Diluition unitOutermost shield

Page 27: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

The CUORE program

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Cuoricino2003-2008

M· T (130Te) = 19.75 kg.yr B = 0.169 ± 0.006

c/keV/kg/y∆ = 6.3 ± 2.5 keV FWHM

T1/2 > 2.8· 1024 y (90% C.L.)

CUORE2015-2020

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

Page 28: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

Beyond CUORE

Next generation bolometric experiment for 0νββ searches aims to use active rejection techniques to drastically reduce the background:

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CUORE Upgrade with Particle ID (CUPID)

TMaT 00B

BTM

TMaTB

0

arXiv:1504.03599

Page 29: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

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.

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Page 30: First neutrinoless double beta decay results from CUORE-0 L. Gironi on behalf of the CUORE collaboration Università degli Studi di Milano - Bicocca INFN.

Luca Gironi Prague, June 09th - 12th, 2015

The CUORE Collaboration

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