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CUORE: Cryogenic Underground Observatory for Rare Events

CUORE is a cryogenic underground observatory designed for the detection of rare events. It features cryogenic detectors with good energy resolution and a wide choice of detector materials. The observatory will be closely packed with 988 detectors made of TeO2, with a total mass of 741 kg. It aims to achieve high sensitivity and detect events above background noise at a given confidence level.

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CUORE: Cryogenic Underground Observatory for Rare Events

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  1. CUORE:Cryogenic Underground Observatory for Rare Events Carlo Bucci INFN – Laboratori Nazionali del Gran Sasso on behalf of the CUORE collaboration LAUNCH, Heidelberg 21-23 March 2007

  2. Heat bath (~8 mK) Weak thermal coupling (G~4 pW/mK) Thermometer (NTD Ge , R~100 MΩ) Adsorber crystal (TeO2, C~10-9 J/K) Cryogenic Detectors Cryodet features ▲ wide choice of detector materials ▲ good energy resolution ▲ true calorimeters ▼ speed LAUNCH, Heidelberg 21-23 March 2007

  3. Measurement Time (y) Detector mass (kg) Efficiency Isotopic abundance 1/2 Energy resolution (keV) a M T S0n=ln 2 NA´ ´e A bG Atomic mass Background (counts/keV/kg/y) Unavoidable background sum electron energy / Q DDB-0n Sensitivity Sensitivity: Lifetime corresponding to the minimum number of detectable events above background at a given C.L. LAUNCH, Heidelberg 21-23 March 2007

  4. Isotopic abundance (%) Transition energy (MeV) 5 40 4 20 3 2 0 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd 48Ca 76Ge 82Se 96Zr 100Mo 116Cd 130Te 136Xe 150Nd TeO2 cryogenic detectors Active isotope 130Te ▲ high natural isotopic abundance: a =33.4 % ▲ transition energy: Q = 2530 keV ▲ reasonable nuclear matrix element calculations TeO2 Absorbers ▲ low specific heat ▲ large crystals available ▲ radiopure LAUNCH, Heidelberg 21-23 March 2007

  5. CUORE R&D (Hall C) Cuoricino (Hall A) CUORE (Hall A) CUORE @ LNGS LAUNCH, Heidelberg 21-23 March 2007

  6. Cryogenic Underground Observatory for Rare Events CUORE will be a closely packed array of988 detectors M =741 kgof TeO2 • Special cryostat & dilution unit • Cryogenic liquids free: 5 Pulse Tubes with …40W @ 45K & 1.5 W @ 4.2K • JT cycle instead of the 1K Pot • Dimensions: 1.6 m Ø x 3 m • (almost) all in Copper for radiopurity • huge mass to cooldown (mainly Pb shielding) • 1.5 ton @ 10mK • 6 ton @ 50 mK • 4 ton @ 600 mK • 5 ton between 40 & 4 K 80 cm 19 towers with 13 planes of 4 crystals each LAUNCH, Heidelberg 21-23 March 2007

  7. Pulse tubes 25 cm Pb 300 K 20 cm PET 4 K 50 mK 50 K 4He/3He Dilution Unit 600 mK 33 cm Pb shield (4 ton) 5 mK 3 cm Pb shield (3 ton) Cuore 3 cm Roman Pb shield (2 ton) 1600 CUORE cryostat LAUNCH, Heidelberg 21-23 March 2007

  8. CUORE Hut LAUNCH, Heidelberg 21-23 March 2007

  9. CUORE expected sensitivity In 5 years: Strumia A. and Vissani F. - hep-ph/0606054 LAUNCH, Heidelberg 21-23 March 2007

  10. Moore’s Law CUORE Cuoricino Mibeta 4 detectors array 340 g 73 g 1985 1990 1995 2000 2005 2010 2015 LAUNCH, Heidelberg 21-23 March 2007

  11. Cuoricino 11modules 4 detectors each Dimension:5x5x5 cm3 Mass:790 g Total mass 40.7 kg 2 modules 9 detectorseach, Dimension:3x3x6 cm3 Mass:330 g LAUNCH, Heidelberg 21-23 March 2007

  12. Detectors assembling All the operations done in Clean Room and nitrogen atmosphere LAUNCH, Heidelberg 21-23 March 2007

  13. Cuoricino module Ge NTD thermistor A Cuoricino module LAUNCH, Heidelberg 21-23 March 2007

  14. Tower assembling LAUNCH, Heidelberg 21-23 March 2007

  15. 2615 keV 208Tl single escape double escape 232Th Calibration Sum spectrum of all the 5x5x5 cm3 detectors DEFWHM =7.5 keV@2615 keV LAUNCH, Heidelberg 21-23 March 2007

  16. Live time Run I Cooldown: February 2003 Detectors: 14/62 detectors lost Working detectors: 73% Live Time: 23% • Upgrade: October 2003 • Wiring • DAQ • Temperature feedback • Cryogenics (20 years old cryostat) Run II Cooldown: May 2004 Detectors: 2 detectors still dead + 1 with high noise Working detectors: 95% Live Time: 60% (+ ~ 10% calibrations time) But many many hours lost due to high vibrational noise caused by the works underway in LNGS LAUNCH, Heidelberg 21-23 March 2007

  17. Background • Flat background above 2615 keV • Natural extrapolation below • Contribution to the 0n-DBD region: ~ 70%(degraded a from Copper & TeO2 surfaces) • In R&D already decreased by a factor ~ 4 LAUNCH, Heidelberg 21-23 March 2007

  18. 0n-DBD Background • Contribution from 232Th to DBD region ~ 30% • Internal shielding far from optimal (cryostat too small) • In CUORE should be much lower LAUNCH, Heidelberg 21-23 March 2007

  19. 0n-DBD peak @2530.3 keV 60Co sum peak Counts Energy [keV] * Dependent on the value for the nuclear matrix elements Cuoricino result on 130Te bb-0n decay Total statistic11.8 kg (130Te) × y b = 0.18 ± 0.01c/keV/kg/y Maximum Likelihood flat background + fit of 2505 peak Anticoincidence background spectrum the bb-0nregion LAUNCH, Heidelberg 21-23 March 2007

  20. KK-HM evidence (best value 0.44 eV) Cuoricino limit (with the same NME <0.41 eV) In 3 years running time t1/20nbb>5.2⋅1024y @ 90C.L. <mbb>< 0.12-0.64 eV Cuoricino result Strumia A. and Vissani F. - hep-ph/0606054 LAUNCH, Heidelberg 21-23 March 2007

  21. Cuoricino discovery potential <mn>=50 meV – half lives for different nuclei and models [1026 y] Elliot-Vogel 2002 Rodin et al. Suhonen et al. LAUNCH, Heidelberg 21-23 March 2007

  22. Conclusions • Cuoricino is presently the most sensitive DBD-0n running experiment, capable to hopefully confirm in a relatively short time the KK-HM “evidence”. • Cuoricino demonstrate the feasibility of a large scale bolometric detector with good energy resolution and background. • The costruction of CUORE, a second generation detector, is started and we plan to start taking data in less than 4 years from now. CUORE will have the capability to explore the inverse hierarchy mass region. LAUNCH, Heidelberg 21-23 March 2007

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