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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

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From CUORICINO to CUORE: To probe the inverted hierarchy region

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  1. 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 DUSL Meeting, Washington DC November 2,-4, 2007

  2. ITALY UNITED STATES The CUORE collaboration

  3. 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

  4. 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

  5. 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 = ( 7 - 27 )  1020 y) • 2n DBD decay observed by a precursor bolometric experiment (MIBETA) and by NEMO-3 at the level  1/2= (7.6 )  1020 y

  6. The bolometric technique for 130Te: detector concepts

  7. Thermometer (Neutron transition doped Ge chip) • Energy absorber • single TeO2 crystal • 790 g • 5 x 5 x 5 cm Tellurium oxide bolometers for DBD

  8. 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)

  9. 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

  10. 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]

  11. 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

  12. 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

  13. CUORE funding and schedule • CUORE has a dedicated site in LNGS and construction of the site • has started • The CUORE refrigerator has been funded and is on order • 1000 crystals: Funding by INFN (500 already ordered) • and 500 to be purchased by LLNL with US DOE funding • The CUORE Electronics: Funded in Sept. 07 by the NSF via • The University of South Carolina First CUORE tower “CUORE-0" assembled in 2008 and operated in 2009 in CUORICINO Cryostat CUORE scheduled to begin in January 2011

  14. 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

  15. ~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

  16. 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

  17. 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

  18. (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

  19. 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) = (0.91-3.6)  1025 (3σ range) Klapdor-Kleingrothaus et al. Modern Physics Letters A21(2006) 1547. Best value: 2.23x1025 y Nuclear matrix element of Rodin et al., Erratum nucl-th/0706.4304 mββ= 0.23 – 0.51 eV (3σ range)

  20. QRPA Tuebingen-Bratislava -Caltech group: erratum: nucl-th/0706.4304 • Civitarese and Suhonen: Nucl. Phys. A 761(2005) 313. • Shell Model: E. Caurier et al., nucl-th:0709.0277 Compare experiments with different isotopes T1/20v (Klapdor et al.) Choose a nuclear model T1/20v (130Te) Use three recent nuclear structure models:

  21. KKDK DISCOVERY RANGE: CUOICINO 90%LOWER BOUND CUORICINO SENSITIVITY DISCOVERY RANGE IS Te-130 EQUIVELENT Ranges:

  22. 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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