Status of CUORE and Results from CUORICINO. SERGIO DI DOMIZIO UNIVERSITÀ & INFN GENOVA On behalf of the CUORE Collaboration

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1 Status of CUORE and Results from CUORICINO SERGIO DI DOMIZIO UNIVERSITÀ & INFN GENOVA On behalf of the CUORE Collaboration 11th Seminar on Innovative Particle and Radiation Detectors Siena, 1 October 2008

2 Outline Double Beta Decay Process description Scientific content Experimental features CUORE & CUORICINO Double Beta Decay with Bolometers CUORICINO: detector description and latest results The CUORE experiment current status of CUORE 2

3 Neutrino Open Questions Normal hierarchy Inverted hierarchy What we know What is still missing Neutrinos have mass Neutrinos mix Almost all the Mixing matrix elements have been measured m2sun and m2atm have been measured The absolute mass scale The sign of m 2ATM (hierarchy) Whether neutrinos are Dirac or Majorana particles If lepton number is not conserved, then neutrino is a neutral fermion: can be described by a Majorana field 3

4 Double Beta Decay Double beta decay is a rare process in which a nucleus changes its atomic number by 2 units 2 : A, Z A, Z 2 2e 2 Allowed by standard model Observed for several isotopes 0 : A, Z A, Z 2 2e Forbidden by standard model Allowed only for Majorana neutrinos Never observed 4

5 0 Decay Time experiments can measure the decay time T 0 1/2 Nuclear matrix element phase space (theoretical uncertainty) 2 0 m = 0 = G Q, Z M NUCL m = F N T 1/2 m2e effective Majorana Mass Observation of would prove that: lepton number is not conserved m [ev] m = mi U2ei neutrinos are Majorana particles could give informations on the absolute scale of neutrino masses mass of lightest neutrino [ev] Strumia, Vissani arxiv:hep-ph/

6 0 in Experiments Signature: All the energy is shared between the 2 electrons: monochromatic line at the Q-value of the decay detector mass Sensitivity S 0 isotopic abundance decay time corresponding to the minimum number of detectable events above background S 0 live time Mt a b E Background counts energy resolution 6

7 CUORE & CUORICINO CUORE and CUORICINO are bolometric detectors for the search of decay of 130Te CUORE will search for decay in the inverted mass-hierarchy region CUORICINO is a small prototype of CUORE Completed in June 08 HALL A Cuore & Cuoricino Located in the underground Gran Sasso National Labs: 3400 w.m.e. shield against cosmic rays HALL C Cuore R&D cryogenic facility 7 7

8 Bolometers Principle: measure the temperature rise of the energy absorber E T = : requires low temperature and low heat capacity C Thermal bath: ~ 8 mk Absorber Weak thermal coupling (dielectric & diamagnetic xtal) M ~ 790 g C ~ 10-9 J/K T/E ~ 0.2 mk/mev Energy release Sensor (NTD thermistor) R ~ 100 M (dr/dt) dr/dt ~ 100 k / K Output signal: ~ 100 V / MeV 8

9 TeO2 Bolometers for 0 CUORE and CUORICINO use TeO2 crystals: source detector decay: why Te 130Xe + 2e- 130 Te 130 High isotopic abundance: 34% no need for enrichment Q-value: ~ 2530 kev: almost above natural background why TeO2 Easy to grow big crystals with low radioactive contaminations Good mechanical properties Low heat capacity 9

10 CUORICINO Diluition refrigerator (Coldest point ~ 8mK) Detector: a tower of 62 TeO2 crystals Mass: 42 Kg (11.8 Kg in 130Te) 11 floors made of 4 crystals not enriched Mass: 790g Dimensions: 5x5x5 cm3 Shielding Internal: External: 1cm low activity Pb 20cm Pb 20cm Borated Polyethylene Anti-Rn box: Nitrogen overpressure (A < 4 mbq/kg in 210Pb) 2 floors made of 9 crystals: Mass: 330g Dim: 3x3x6 cm3 2 enriched in 128Te (82%) 2 enriched in 130Te (75%) 10

11 CUORICINO Calibration 3 days every 1 month: 232 Th source Sum calibration spectra 5 x 5 x 5 crystals Average resolution: ~ keV 11

12 CUORICINO Results 60 Statistics M t = kg y in (up to August 07) Co Te Background 0.18 counts/kev/kg/yr No signal found T 0 1/ 2 > C.L. Phys. Rev. C 78 (2008) m < ev (Nuclear Matrix Element: Nucl. Phys. A 766 (2006) + erratum nucl th/ ) 12

13 CUORE Cryogenic Underground Observatory for Rare Events Total mass:741 Kg 130 Te: 203 Kg 80cm 988 TeO2 crystals 19 towers 13 floors 52 crystals each 13

14 CUORE Sensitivity Expected CUORE sensitivity in 5 years T 1/ C.L. m mev CUORE m [ev] Background 0.01 c/kev/kg/y CUORICINO mass of lightest neutrino [ev] 14

15 CUORICINO Background Co 208 Tl Bi degraded Background contributions 60Co from Cu cosmogenic activation: negligible Multi-Compton from 208Tl (232Th cont. in cryostat shields): ~40% Degraded from crystal surfaces: ~10% Degraded from Cu holders surfaces: ~50% Muon-induced background: negligible 15

16 CUORE Background Tests in HALL C R&D facility reduction by a factor ~4 on Crystal surf. contaminations Reduction by a factor ~2 on Cu frames surf. contaminations Component Projection to CUORE (goal: 10-2 c/kev/kg/y) Bkg in DBD region [10-2 c/kev/kg/y] Environmental < 0.1 Apparatus < 0.1 Crystal bulk < 0.01 Crystal surface < 0.3 Cu frames bulk < 0.1 Cu frames surface ~2 4 Neutrons < 0.01 Muons <

17 The Three Towers Test Test the best Cu cleaning procedure Few months data taking, start in Nov 08 Use CUORICINO cryostat Legnaro Cleaning: TECM Tumbling Electropolishing Chemical etching Magnetron sputtering LNGS Cleaning Electropolishing Chemical etching Passivation Alternative LNGS Cleaning Electropolishing Chemical etching Passivation Cu frames covered with 50 m PET foil 17

18 CUORE Status CUORE-0 The first tower of CUORE will be assembled and operated in 2009: Test zero-contact assembling approach Same mechanical design as CUORE towers Will be hosted in CUORICINO cryostat CUORE Hut construction Crystal production started First batch will arrive in November 08 Diluition refrigerator is being built data taking is foreseen in

19 Conclusions Observation of decay would prove that neutrinos are Majorana particles Bolometers are a powerful technique for the search of Double Beta Decay CUORICINO has demonstrated the feasibility of CUORE and has set a limit on the decay time of 130Te CUORE construction has started: data taking is foreseen in