The cuore experiment a search for neutrinoless double beta decay
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The CUORE EXPERIMENT: A search for neutrinoless double beta decay. 2 nd International Conference on Particle Physics in Memoriam Engin Arık and Her Colleagues Istanbul, Turkey 20 - 25 June 2011. Marco Andrea Carrettoni on behalf of the CUORE collaboration. Outline.

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The CUORE EXPERIMENT: A search for neutrinoless double beta decay

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The cuore experiment a search for neutrinoless double beta decay

The CUORE EXPERIMENT: A searchforneutrinolessdouble beta decay

2nd International Conference on Particle Physics

in Memoriam EnginArık and Her Colleagues

Istanbul, Turkey

20 - 25 June 2011

Marco Andrea Carrettoni on behalfof the CUORE collaboration


Outline

Outline

  • Theoretical and experimentalcontext:

    • NeutrinolessDouble Beta Decay (0n-DBD)

    • Sensitivity

    • BolometricApproach

  • The CUORE experiment

    • Set-up and properties

  • CUORICINO: the demonstrator

  • On the road to CUORE: CUORE-0

  • Conclusions


Why neutrinoless double beta decay

WhyNeutrinolessDouble Beta Decay?

Effective

Majorana

Mass

Nuclearmatrixelement

DBD rate

Phasespace


Probing the neutrino mass

Probing the neutrino mass

Strumia&Vissanihep-ph/0503243


Signature and sensitivity

dN/dE

Signature and sensitivity

In a source=detectorapproachweexpect a peak at the q-value Q of the transition (energy sum of the twoelectrons)

Q

Electrons energy

Sensitivity: Defined as the decay time corresponding to the minimum number of detectable events above a background (B) at a given C.L.


Bolometric approach

Bolometricapproach

6

  • IdealCalorimeter: Energy tophononsconversion

Thermalbath (copper)

@ 10mK

Weakthermalcoupling

(Teflon)

NTD Ge thermistor

R100 MW

TeO2 Crystal Absorber

C  10-9 J/K

  • Pros:

  • Highresolutions

  • Wide choiceofmaterials

  • Cons:

  • Slow signals

  • No particledistinction

  • Operatingprinciple:

  • Dielectric and diamagneticcrystals: low thermalcapacity @ low temperature


Energy absorber temperature sensor

Energy absorber & temperature sensor

TeO2cubiccrystal

NTD-Gethermistor

  • 5x5x5 cm3

  • - The choice of the material isdrivenby the choice of the candidate nuclide

  • 3x3x1 mm3

  • - Ge dopedbyNeutronTransmutation Doping

TeO2

130Te

1.

~2527 keV

A. Dielectricwith TD=232 K:

C minimized

B.Easy togrowlargecrystalswithgoodradio-purity

C. Resistancetoseries of thermalcycles at very low temperatures

2.

A typicalacquiredparticlesignal


Cuore cryogenic underground experiment for rare events

CUORE (Cryogenic Underground Experimentfor Rare Events)

Pulse Tube

(L He-freecryostat)

  • 988 TeO2crystals 5x5x5cm3 (750g), arranged in 19 towers;

  • 741 kg of TeO2 -> 206 kg of130Te

  • Resolution 5 keV @ 2615 keV (FWHM)

  • Background aim: 0.01-0.001 c/keV/kg/y

  • Mainconcepts:

  • Stringentcontrols on radioactivity

  • Heavyshielded (Roman lead)

  • High efficiency in bkgrejectionthankstoclosepacketgeometry

Polyethilene

(NeutronsShieldings)

CopperShielding

ExternalLead

Shieldings

(210 Po<14 mBq/kg)

Roman LeadShieldings

(210 Po<4 mBq/kg)

Detector


The cuore experiment a search for neutrinoless double beta decay

LNGS

CUOREwillbelocated in the Hall A of the Gran

Sassonationallaboratories (L’Aquila – Italy)

  • Depth: 3650 m.w.e.

  • Muonflux: (2.58±0.3)x10-8m/s/cm2

  • Neutronflux 4x10-6 n/s/cm2

  • Gamma flux: 0.73 g/s/cm2

  • Cosmicrays are not a problem!


The cuore program

The CUORE program

CUORICINO

2003-2008

CUORE – 0

2011 - 2014

CUORE

2014-2019

19 Tower

998 crystals

M 206 kg of130Te

Bkg 0.01 ÷ 0.001 c/keV/kg/yr

1 Tower

62 crystals

M 11 kg of130Te

Bkg  0.15 c/keV/kg/yr

1 Tower

52 crystals

M11 kg of130Te

Bkg 0.05 ÷ 0.1 c/keV/kg/yr


Cuoricino the demonstrator

Cuoricino: the demonstrator

The bolometrictechniquehasbeenappliedto the search of the following 0v-DBD:

130Te 130Xe + 2e-Q0v~2527 keV

The Cuoricino experiment (LNGS, 2003-2008) is the result of years of research on bolometerscontaining130Te, byusing TeO2 energyabsorbers

  • Cryostat

  • LeadShield (20 cm)

  • Neutronshieldofborated

  • Polyethilene

  • Roman LeadShield

  • (210Po < 4mBq/kg)

Mass

40.7 kg TeO2

(11.3 kg 130Te)

Total exposure

19.75 kg y [130Te]] y


Cuoricino main operating principle

Cuoricino mainoperatingprinciple

  • The analysisiscarried out on anti-coicinidencespectra in orderto reduce:

    • Contributionfromcrystalsurfaces

    • Compton or multi-comptonevents

  • Accidentalcoincidences 0.7%

  • Bkgreduction : 15%

TeO2

TeO2

Single Hit EventsDouble Hit Events

TeO2


0 n dbd region of interest

0n-DBD regionof interest

  • The anti-coincidencespectrum in the regionof interest showsthreemainpeaks:

    • 208Tl : (probably in the cryostat)

    • 60Co: cosmogenicorigin

    • 214Bi: Rncontamination

  • The main background contributions are:

    • Multicomptoneventsof208Tl (30%)

    • Flat background comingfromdegradedalphas on the surfaceofmaterialsfacing the crystals

    • (70%)

R.O.I.

214Bi

208Tl

60Co (g+g)

Flat continuum

0nDBD

Normalizedcalibration

escaped Te X-ray


Cuoricino result astropart phys 2011 doi 10 1016 j astropartphys 2011 02 002

Cuoricino ResultAstropart. Phys. (2011), doi:10.1016/j.astropartphys.2011.02.002

Method:

  • Best fit: maximumlikelihood-chisquare

  • Limit: bayesian (flatprior on G0n)

    Avg Background in the regionof interest:

    0.169±0.006 c/keV/kg/y

    Avgresolutio: ∆E7 keV FWHM

mee<300-701meV*

t0nbb1/2 > 2.8x1024 y @ 90% CL

UUnphysical

region

  • * Spread introducedby NME

60Co


Two parallel analysis validation on monte carlo

Twoparallelanalysis: validation on Monte Carlo

  • Twoindepententanalysiswerecarried out on data and simulationwithanexeptional agreement

  • Both the methodsprovedtobeunbiased and robust.

  • On the simulations (1000 Cuoricino-likeexperiments) they show a wide distributionofpossibleoutcomes.

  • The medianoutcomeoftheseexperimentscorrespondsto a limit on the half life of 2.6x1024 y comparableto the experimentallimit


From cuoricino to cuore

From Cuoricino to CUORE

  • Extensivestudyof the background sources

  • Design of the experiment

  • Cryostat and shieldings

  • Radioactivitycontrol

  • Electronics

  • DAQ

  • Crystals

  • Software

  • Calibration system

  • Towerassembly

Challengingeffort on

everycrucialaspectsof

the experiments


Cuore crystals

CUORE Crystals

The 1000 CUORE crystals are producedby SICCAS

(Shanghai, China):

- 560 crystalsorderedby INFN ([email protected]);

- 500 crystalorderedbyDoE (91 already in

@LNGS, end in Sept. 2012)

Foreach production batch 2 or more crystals are

tested in the Hall C R&DCryostat:

- Same single moduleas CUORE;

- New Data Acquisition and online as CUORE;

- All material cleanedCUORE-like;

6 CCVR measurementswereanalyzed (preliminaryresults):

Surface : < nBq/cm2

Resolution : avg ∆E = (4.9 ± 1.9) keV FWHM

preliminary

< 6 · 10−14 g/g in 238U

< 8 · 10−14 g/g in 232Th

Bulk:

Production requirements

perfectlyfulfilled!


The answer to cuore 0

The answerto CUORE-0

The full assembly of a CUORE-like tower: data taking starts this fall

High statistic test of the background achievements: crucial importance

for surface background studies

Two irreducible background predicted (realistic and optimistic case)

CUORE-0 will be a competitive 0nDBD experiment itself!


Cuore scientific goal

CUORE scientific goal

In 5 years of live time, CUORE has a 1σ sensitivity of tDBD1/2 = 2.1x1026 y ⇒ effective Majorana neutrino mass down to 35 ÷ 82 meV

With the foreseen aim of

0.01 c/keV/kg/y

CUORE will be able to probe

the inverted scale


Conclusions

Conclusions

  • Te02 bolometersprovedtobe a competitive toolfor the DBD search

  • Cuoricino provedtobenotonlyanimportantexperiment, butalso a greatprototype, showingthatanexperimentlike CUORE isfeasible

  • CUORE-0 willbe the first test of a CUORE-liketowerfrom the assemblyto data taking and a competitive experimentitself

  • CUORE data takingisforeseenfor 2014


Conclusions1

Conclusions

Thankyouforyouattention


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