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-0L. Gironi on behalf of the CUORE collaborationUniversit degli Studi di Milano - BicoccaINFN di Milano - Bicocca10th M E D E X '15 meetingPrague, June 09th- 12th, 2015

    Luca GironiPrague, June 09th- 12th, 2015

    Bolometers for 0DBD*Why bolometers are suitable detectors for 0DBD ?

    ParametersBolometersMaximum sensitivity achievable regardless of and B (zero background limit)- Possibility to choose among all the isotope - optimization of a- Very high detection efficiency () (source=detector)Fundamental in 0DBD studies because of the 2DBD- Excellent energy resolution (~5 keV at Q-value)BIn many cases it is still possible to act on it to greatly improve the sensitivity- Possibility to choose among all the isotope - Q-value in low background region- Very low background level already reached but surface contaminations

    Luca GironiPrague, June 09th- 12th, 2015

    TeO2 Bolometric DetectorsAt 10 mK, energy deposited in TeO2 results in a measurable change in temperatureEnergy release T R in the thermistor V130Te is one of the best candidates for 0DBD 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*Ttherm~ 10-20 K/MeVTcryst ~ 0.1 mK/MeV

    Rtherm ~ 3 M/MeVVtherm ~ 0.3 mV/MeV

    Luca GironiPrague, June 09th- 12th, 2015

    The CUORE program*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.)Search for 0DBD of 130Te with TeO2 bolometersM: Scale up mass (~20x)T: Cryogen-free dilution refrigerator: Improve energy resolution B: Reduce background (~20x)

    Luca GironiPrague, June 09th- 12th, 2015

    Cuoricinom < (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)*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/yrT1/2> 2.8 x 1024y (90% C.L.)0 upper limit

    Luca GironiPrague, June 09th- 12th, 2015

    Cuoricino Background*Main sources of background in the ROI:30% Compton from 208Tl decays in cryostat60% Degraded alphas on copper surfaces10% Degraded alphas on crystal surfacesPhysics dataCalibration data

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE-0CUORE-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*

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE/CUORE-0 Assembly line*Clean Room for Detector Assembly and StorageCUORE hutCuoricino/CUORE-0 hutCUORE-0 construction was carried out inside N2-flushed glove boxes in CUORE huts clean room.

    Luca GironiPrague, June 09th- 12th, 2015

    *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

    Luca GironiPrague, June 09th- 12th, 2015

    *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

    Luca GironiPrague, June 09th- 12th, 2015

    *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

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE-0with 10mK shield*CUORE/CUORE-0 Assembly lineThe successful operation of CUORE-0 demonstrated the validity of the CUORE tower assembly line and of the CUORE cleaning procedures.CUOREtowerTower storage

    Luca GironiPrague, June 09th- 12th, 2015

    *CUORE-0 Uses the old Cuoricino cryostat

    Electronics from Cuoricino

    Shielding from Cuoricino

    Cooled to base T (~10 mK) Mar 2013

    Luca GironiPrague, 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*

    Luca GironiPrague, June 09th- 12th, 2015

    *Total fit on the 2615 keV lineDistribution of energy resolution @ 2615 keVCUORE-0 Calibration energy resolutionThe 5 keV CUORE goal has been reachedCUORE-0PreliminaryCUORE-0Preliminary

    Exposure-weightedHarmonic Mean FWHMRMS ofFWHMCuoricino5.8 keV2.1 keVCUORE-04.9 keV2.9 keV

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE-0 Background a factor ~7 reduction in the alpha continuum region s from U chain reduced with radon control residual bkg in ROI from Th cryostat contaminations (negligible in CUORE)

    *Comparison of the total background spectrum in CUORE-0 and CuoricinoCUORE-0 Preliminary

    2.7-3.9 MeV[c/keV/kg/y]eff[%]Cuoricino0.110 0.00183 1CUORE-00.016 0.00181 1

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE-0 0DBD 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:*Pile-up removal: multiple events in the same acquisition window are rejectedPulse shape discrimination: events with unexpected shape are rejectedAnti-coincidence: only single crystals events are signal candidatesTotal selection efficiency = (81.3 0.6)%

    efficiency[%]error [%]Trigger98.5290.004Pile-up and PSA93.70.7Event containment88.40.09Accidental coincidence99.640.10

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE-0 0DBD searchAfter all cuts: 233 events in ROI [2470-2570 keV].*Best value fit of the 0DBD decay rate:0= 0.01 0.12(stat.) 0.01(syst.) x 10-24 yr-1Background index in ROI: 0.058 0.004(stat.) 0.002(syst.) c/keV/kg/yWe find no evidence for a signal and set 90% C.L. lower limit from profile likelihood: Profile negative log-likelihoodCUORE-0 PreliminaryCUORE-0 Preliminary

    Luca GironiPrague, June 09th- 12th, 2015

    *CUORICINO/CUORE-0 combined limitWe combine the CUORE-0 result with the existing 19.75 kg yr of 130Te exposure from Cuoricino This is the most stringent limit on this half-life !Profile negative log-likelihoodCUORE-0 Preliminary

    Luca GironiPrague, June 09th- 12th, 2015

    *Extrapolation to mCombined half-life result as a limit on the effective Majorana neutrino mass:m < (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

    Luca GironiPrague, June 09th- 12th, 2015

    The CUORE program*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 0DBD of 130Te with TeO2 bolometersM: Scale up mass (~20x)T: Cryogen-free dilution refrigerator: Improve energy resolution B: Reduce background (~20x)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.)

    Luca GironiPrague, 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):*

    Luca GironiPrague, June 09th- 12th, 2015

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

    * 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 flangesInternal lead shield (low-radioactivity/ancient lead)

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE Self shielding* CUORE-0: All bolometers face 10 mK shield CUORE: Only outermost crystals face 10 mK shield

    Luca GironiPrague, June 09th- 12th, 2015

    CUORE StatusAssembly of the 19 CUORE towers is complete*Expect to deploy the array in the cryostat later this year.

    Luca GironiPrague, 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*Plan to start operations by end of 2015.Outermost shield

    Luca GironiPrague, June 09th- 12th, 2015

    The CUORE program*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

    Luca GironiPrague, June 09th- 12th, 2015

    Beyond CUORENext generation bolometric experiment for 0 searches aims to use active rejection techniques to drastically reduce the background:*CUORE Upgrade with Particle ID (CUPID)arXiv:1504.03599

    Luca GironiPrague, June 09th- 12th, 2015

    ConclusionsTeO2 bolometers offer a well-established, competitive technique in the search for 0DBD

    CUORE-0 Achieved its energy resolution and background level goals. Indicated CUORE sensitivity goal is within reach. Did not find evidence of 130Te 0DBD 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.*

    Luca GironiPrague, June 09th- 12th, 2015

    The CUORE Collaboration*