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From CUORICINO to CUORE: To probe the inverted hierarchy region. Frank Avignone University of South Carolina and INFN Laboratori Nazionali del Gran Sasso. On behalf of the CUORE collaboration

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From cuoricino to cuore to probe the inverted hierarchy region

From CUORICINO to CUORE:

To probe the inverted hierarchy region

Frank Avignone

University of South Carolina

and

INFN Laboratori Nazionali del Gran Sasso

On behalf of the CUORE collaboration

Adapted from Andrea Giuliani’s TAUP presentation

Sendai Japan, September 11-15, 2007


From cuoricino to cuore to probe the inverted hierarchy region

ITALY

UNITED STATES

The CUORE collaboration


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics/experimental techniques

  • 130Te bolometers

  • Structure of CUORICINO, present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO/CUORE potential according to recent

    nuclear structure calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

2n Double Beta Decay

allowed by the Standard Model

observed : = 1019 -1021y

neutrinoless Double Beta Decay (0n-DBD)

never observed (except KKDK claim)

> 1025 y

(A,Z)  (A,Z+2) + 2e-

(A,)  (A,Z+2) + 2e- + 2ne

Decay modes for Double Beta Decay


From cuoricino to cuore to probe the inverted hierarchy region

Electron sum energy spectra in DBD

two neutrino DBD

continuum with maximum at ~1/3 Q

neutrinoless DBD

peak enlarged only by

the detector energy resolution

sum electron energy / Q

The shape of the two electron sum energy spectrum enables us to distinguish between the two decay modes


From cuoricino to cuore to probe the inverted hierarchy region

detector

e-

source

e-

detector

SourceDetector

SourceDetector

calorimetric technique

Fiorini 1967 Ge, 1984,Te

  • scintillation (Elegants, MOON)

  • gaseous/foil TPC (Moe)

  • gaseous drift chamber

    with magnetic field and

    calorimetry (NEMO-3)

  • scintillation (Zdesenko)

  • solid-state devices (Ge)

  • gaseous/liquid TPC (EXO)

  • cryogenic macrocalorimeters

  • (bolometers) CUORE/CUORICINO

e-

e-

Event reconstruction

Relatively low efficiency

Energy resolution ~1%

Restricted in background identification

High efficiency

Energy resolution~ 0.1%

Experimental approaches to direct searches

Two approaches for the detection of the two electrons:


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics and experimental issues

  • 130Te bolometers

  • Structure of CUORICINO, present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO and CUORE potential according

    to recent nuclear calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

130Te as a DBD candidate

Large natural abundance

Low-cost

Expandability of Double-Beta Decay experiments

  • high natural isotopic abundance (nat. abundance = 33.87 %)

  • high transition energy (Q = 2530 keV)

  • encouraging theoretical matrix element

  • observed with geo-chemical techniques

    ( 1/2incl = ( 0.7 - 2.7 )  1021 y)

  • 2n DBD decay observed by a precursor bolometric experiment (MIBETA)

    and by NEMO-3 at the level  1/2= (7.6 )  1020 y


From cuoricino to cuore to probe the inverted hierarchy region

The bolometric technique for 130Te: detector concepts


From cuoricino to cuore to probe the inverted hierarchy region

Thermometer

(Neutron transition doped Ge chip)

  • Energy absorber

  • single TeO2 crystal

  • 790 g

  • 5 x 5 x 5 cm

Tellurium oxide bolometers for DBD


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics and experimental issues

  • 130Te and bolometers

  • Structure of CUORICINO and present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO and CUORE potential according to recent nuclear calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

R&D final tests for CUORE (hall C)

CUORICINO/CUORE Location

CUORICINO experiment installed in

Laboratori Nazionali del Gran Sasso

L'Aquila – ITALY

the mountain provides a 3500 m.w.e. shield against cosmic rays

CUORE

(hall A)

CUORICINO

(hall A)


From cuoricino to cuore to probe the inverted hierarchy region

Coldest point

Cold finger

Tower

Lead shield

Same cryostat

and similar

structure

as previous

pilot experiment

The CUORICINO structure

CUORICINO = tower of 13 modules,

11 modules x 4 detector (790 g) each

2 modules x 9 detector (340 g) each

M = ~ 41 kg  ~ 5 x 1025130Te nuclei


From cuoricino to cuore to probe the inverted hierarchy region

Detector performance

  • Performance of CUORICINO detectors (555 cm3- 790 g):

  • Detector base temperature: ~ 7 mK

  • Detector operation temperature: ~ 9 mK

  • Detector response: ~250 mV/ MeV

  • FWHM resolution: ~ 3.9 keV @ 2.6 MeV

238U + 232Th calibration spectrum

60

214Bi

Counts (/1.2 keV)

228Ac

40K

208Tl

10

0.6

1.6

2.6

Energy [MeV]


From cuoricino to cuore to probe the inverted hierarchy region

CUORICINO results

60Co sum peak

2505 keV

~ 3 FWHM from

DBD Q-value

MT = 11.83 kg 130Te  y

Bkg = 0.18±0.02 c/keV/kg/y

Average FWHM resolution

for 790 g detectors: 7 keV

130Te

0nbb

Rodin et al. nucl-th/0706.4304

Caurier et al., New Shell Model

1/20n(y) > 3.0  1024 y (90% CL )

Mbb< 0.38 – 0.58 eV


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics and experimental issues

  • 130Te and bolometers

  • Structure of CUORICINO and present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO/CUORE potential according to recent nuclear calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

CUORE = close-packed array of 988 detectors

19 towers - 13 modules/tower - 4 detectors/module

M = 741 kg~ 1027130Te nuclei

Compact structure, ideal for active shielding

Each tower is a CUORICINO-like detector

Special dilution refrigerator

From CUORICINO to CUORE(Cryogenic Underground Observatory for Rare Events)

and granularity


From cuoricino to cuore to probe the inverted hierarchy region

CUORE funding and schedule

  • CUORE has a dedicated site in LNGS and the construction of site started

  • The CUORE refrigerator is fully funded and has been ordered

  • 1000 crystals: promised funding by INFN and US DOE

  • The CUORE Electronics will be funded by the NSF via USC

First CUORE tower “CUORE-0" assembled in 2008

and operated in 2009 in CUORICINO Cryostat

CUORE scheduled to begin in January 2011


From cuoricino to cuore to probe the inverted hierarchy region

Montecarlo simulations of the background show that

b ~ 0.001 counts / (keV kg y)

is possible with the present bulk contamination of the bolometers

The problem is surface background (energy-degraded alpha, beta)

must be reduced by more than a factor of 10

below that of CUORICINO: work in progress!

10 y sensitivity (1 s) with conservative

Assumption: b = 0.01 counts/(keV kg y)

FWHM = 10 keV

10 y sensitivity (1 s) with aggressive

assumption: b = 0.001 counts/(keV kg y)

FWHM = 5 keV

Mbb< 23-33 meV

QRPA-SM

Mbb< 38-58 meV

QRPA-SM

CUORE sensitivity


From cuoricino to cuore to probe the inverted hierarchy region

~50 meV

~20 meV

Inverted hierarchy band

CUORE and the inverted hierarchy region

Mbb

S. Pascoli, S.T. Petcov

Quasi-degenarate

Inverted hierarchy

Normal hierarchy

Lightest neutrino mass


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics and experimental issues

  • 130Te and bolometers

  • Structure of CUORICINO and present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO and CUORE potential according to recent nuclear calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

Monte Carlo simulation of the CUORE background based on:

  • CUORE baseline structure and geometry

  • Gamma and alpha counting with HPGe and Si-barrier detectors

  • CUORICINO experience  CUORICINO background model

  • Specific measurements with dedicated bolometers in test DR in LNGS

Results…..

The CUORE background model

Sources of the background

  • Radioactive contamination in the detector materials (bulk and surface)

  • Radioactive contamination in the set-up, shielding included

  • Neutrons from rock radioactivity

  • Muon-induced neutrons


From cuoricino to cuore to probe the inverted hierarchy region

The CUORE background components

Background in DBD region

( 10-3 counts/keV kg y )

Component

Environmental gamma

< 1

Apparatus gamma

< 1

The only limiting factor

Crystal bulk

< 0.1

Crystal surfaces

< 3

Close-to-det. material bulk

< 1

Close-to-det. material surface

~ 20 – 40

Neutrons

~ 0.01

Muons

~ 0.01


From cuoricino to cuore to probe the inverted hierarchy region

The CUORICINO background and the surface radioactivity model

208Tl

214Bi

60Co

p.u.

~ 0.11 c / keV kg y

Gamma region


From cuoricino to cuore to probe the inverted hierarchy region

Additional

component required

here

Reconstruction of the CUORICINO spectrum

in the region 2.5 – 6.5 MeV

0nDBD


From cuoricino to cuore to probe the inverted hierarchy region

The additional component:

inert material surface contamination

In order to explain the 2.0 - 4 MeV region BKG, one has to introduce

238U or 210Pb surface contamination of the copper structure facing the detectors


From cuoricino to cuore to probe the inverted hierarchy region

(A) Passive methods  surface cleaning

(B) Active methods ( “reserve weapons” and diagnostic) events ID

surface sensitive bolometers

scintillating bolometers able

to separate a from electrons

Strategies to control surface background

  • Mechanical action

  • Chemical etching / electrolitic processes

  • Surface passivation


From cuoricino to cuore to probe the inverted hierarchy region

Outline

  • Double Beta Decay: physics and experimental issues

  • 130Te and bolometers

  • Structure of CUORICINO and present results

  • From CUORICINO to CUORE

  • The background: model, investigation and solution

  • CUORICINO and CUORE potential according to recent nuclear calculations

  • Conclusions


From cuoricino to cuore to probe the inverted hierarchy region

Can CUORICINO challange the KKDK claim of evidence?

CUORICINO and the KKDK claim of evidence

Evidence of decay of 76Ge claimed by a subset of the Heidelberg-Moscow collaboration (Klapdor-Kleingrothaus et al.)

T1/20v (y) = (0.69-4.18)  1025 (3σ range)

Klapdor-Kleingrothaus et al.

Physics Letters B 586 (2004) 198-212, Nuc. Instrum. Meth.,A 522, 371(2004).

Best value: 1.19x1025 y

Nuclear matrix element of Rodin et al., Erratum

nucl-th/0706.4304

mββ= 0.22 – 0.58 eV (3σ range)


From cuoricino to cuore to probe the inverted hierarchy region

  • QRPA Tuebingen-Bratislava -Caltech group: erratum: nucl-th/0706.4304

  • QRPA Jyväskylä group: nucl-th/0208005

  • Shell Model: Poves’ talk @ 4th ILIAS Annual Meeting - Chambery

Compare experiments with different isotopes

T1/20v

(Klapdor et al.)

Choose a nuclear model

T1/20v (130Te)

T1/2(76Ge)=1.19 x 1025y equivelent to T1/2(130Te) = 3 x 1024y, CUORICINO bound

Use three recent nuclear structure models:


From cuoricino to cuore to probe the inverted hierarchy region

Present limit

Final sensitivity

7x1024 y

3x1024 y

CUORICINO and the 76Ge claim of evidence

The KKDK claim half life range (3s) is converted into a corresponding range for 130Te using the three mentioned models

Nuclear models

QRPA Tuebingen et al.

Shell model

QRPA Jyväskylä et al.

T1/2 x 1024 y for 130Te


From cuoricino to cuore to probe the inverted hierarchy region

ERRATUM

Since this analysis we have learned that we missed a

New analysis by Klapdor-Kleingrothaus and Krivosheina

That included only pulse shape analysis data. The new

Half life from Heidelberg-Moscow Experiment data is

This will make it a bit more difficult to confirm or refute this result with CUORICINO with one QRPA, but a bit more readibly with Shell model matrix elements.

Thank you Vladimir Tretyak for pointing that out!


From cuoricino to cuore to probe the inverted hierarchy region

Montecarlo simulations of the background show that

b ~ 0.001 counts / (keV kg y)

is possible with the present bulk contamination of the bolometers

The problem is surface background (energy-degraded alpha, beta)

must be reduced by more than a factor of 10

below that of CUORICINO: work in progress!

10 y sensitivity (1 s) with conservative

Assumption: b = 0.01 counts/(keV kg y)

FWHM = 10 keV

10 y sensitivity (1 s) with aggressive

assumption: b = 0.001 counts/(keV kg y)

FWHM = 5 keV

Mbb< 23-33 meV

QRPA-SM

Mbb< 38-58 meV

QRPA-SM

CUORE sensitivity


From cuoricino to cuore to probe the inverted hierarchy region

~50 meV

~20 meV

Inverted hierarchy band

CUORE and the inverted hierarchy region

Mbb

S. Pascoli, S.T. Petcov

Quasi-degenarate

Inverted hierarchy

Normal hierarchy

Lightest neutrino mass


From cuoricino to cuore to probe the inverted hierarchy region

Conclusions

  • Bolometers represent a well established technique, very competitive for

  • neutrinoless DBD search

  • CUORICINO and NEMO-3 are presently the most sensitive 0n DBD running experiments, with chance to confirm the HM claim of evidence if this is correct

  • CUORICINO demonstrates the feasibility of a large scale bolometric

    detector (CUORE) with good energy resolution and background

  • CUORE is a next generation detector; it is funded and is scheduled to begin operation in January 2011

  • Recent results on background suppression confirm the capability to

    explore the inverted hierarchy mass region with CUORE


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