status of cuore and results from cuoricino · 2008-09-29 · status of cuore and results from...
TRANSCRIPT
Status of CUORE and Results from CUORICINO
SERGIO DI DOMIZIOUNIVERSITÀ & INFN GENOVA
On behalf of the CUORE Collaboration
11th Seminar on Innovative Particle and Radiation DetectorsSiena, 1 October 2008
1/10/2008 2IPRD08 - SERGIO DI DOMIZIO
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
1/10/2008 3IPRD08 - SERGIO DI DOMIZIO
Neutrino Open Questions
➔Neutrinos have mass➔Neutrinos mix➔Almost all the Mixing matrix elements
have been measured➔ and have been measured
➔The absolute mass scale➔The sign of (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
m ATM2
What we know What is still missingNormal hierarchy Inverted hierarchy
mSUN2 mATM
2
1/10/2008 4IPRD08 - SERGIO DI DOMIZIO
Double Beta Decay
A, Z A, Z22e−2
A, Z A, Z22e−
● Allowed by standard model● Observed for several isotopes
● Forbidden by standard model● Allowed only for Majorana neutrinos● Never observed
2:
Double beta decay is a rare process in which a nucleus changes its atomic number by 2 units
0:
1/10/2008 5IPRD08 - SERGIO DI DOMIZIO
0 Decay Time
0
=1
T 1/20
= GQ , Z ∣MNUCL∣2∣m∣
2= FN
∣m∣2
me2
m =∑mi Uei2
Nuclear matrix element(theoretical uncertainty)
phase space
experiments can measure the decay time T 1/20
effective Majorana Mass
mass of lightest neutrino [eV]
m [
eV
]
Observation of would prove that:
➔lepton number is not conserved
➔neutrinos are Majorana particles
could give informations on the absolute scale of neutrino masses
Strumia, Vissani arXiv:hep-ph/0606054
1/10/2008 6IPRD08 - SERGIO DI DOMIZIO
0 in Experiments
S0 ∝ a⋅ MtbE
energy resolution
isotopic abundancedetector mass
live time
Background counts
Signature:All the energy is shared between the 2 electrons: monochromatic line at the Q-value of the decay
Sensitivity S0decay time corresponding to the minimum number of detectable events above background
1/10/2008 7IPRD08 - SERGIO DI DOMIZIO
IPRD08 - SERGIO DI DOMIZIO1/10/2008 7
CUORE & CUORICINOCUORE and CUORICINO are bolometric
detectors for the search of decay of 130Te
CUORICINO is a small prototype of CUORE➔Completed in June 08
HALL C
Located in the undergroundGran Sasso National Labs:
3400 w.m.e. shield against cosmic rays Cuore R&D
cryogenic facility
HALL ACuore & Cuoricino
CUORE will search for decay in the inverted mass-hierarchy region
1/10/2008 8IPRD08 - SERGIO DI DOMIZIO
BolometersPrinciple: measure the temperature rise of the energy absorber
Sensor(NTD thermistor)
Absorber(dielectric & diamagnetic xtal)
Thermal bath: ~ 8 mKWeak thermal coupling
Energy release
T =EC
: requires low temperature and low heat capacity
M ~ 790 gC ~ 10-9 J/KT/E ~ 0.2 mK/MeV
Output signal: ~ 100 V / MeVR ~ 100 M (dR/dT)dR/dT ~ 100 k /K
1/10/2008 9IPRD08 - SERGIO DI DOMIZIO
TeO2 Bolometers for 0
why 130Te➔High isotopic abundance: 34%
no need for enrichment➔Q-value: ~ 2530 keV: almost
above natural background
CUORE and CUORICINO use TeO2 crystals: source detector
decay: 130Te 130Xe + 2e-
why TeO2
➔Easy to grow big crystals with low radioactive contaminations
➔Good mechanical properties➔Low heat capacity
1/10/2008 10IPRD08 - SERGIO DI DOMIZIO
CUORICINO
Internal:
Detector: a tower of 62 TeO2 crystalsMass: 42 Kg (11.8 Kg in 130Te)
Diluition refrigerator(Coldest point ~ 8mK)
2 floors made of 9 crystals:●Mass: 330g●Dim: 3x3x6 cm3
●2 enriched in 128Te (82%)●2 enriched in 130Te (75%)
11 floors made of 4 crystals●not enriched●Mass: 790g●Dimensions: 5x5x5 cm3
External:➔20cm Pb➔20cm Borated Polyethylene➔Anti-Rn box: Nitrogen
overpressure
Shielding➔1cm low activity Pb (A < 4 mBq/Kg in 210Pb)
1/10/2008 11IPRD08 - SERGIO DI DOMIZIO
CUORICINO Calibration
Average resolution: ~ 8 keV @ 2615keV
3 days every 1 month: 232Th source
Sum calibration spectra5 x 5 x 5 crystals
1/10/2008 12IPRD08 - SERGIO DI DOMIZIO
CUORICINO Results
StatisticsM·t = 15.53 kg·y in 130Te(up to August 07)
Background0.18 counts/keV/kg/yr
> 3.1· 1024 y @90% C.L.T 1 /20
< 0.20 ÷ 0.68 eV⟨m ⟩(Nuclear Matrix Element: Nucl. Phys. A 766 (2006) + erratum nuclth/0706.4304 )
60Co
0
No signal found
Phys. Rev. C 78 (2008)
1/10/2008 13IPRD08 - SERGIO DI DOMIZIO
Total mass:741 Kg130Te: 203 Kg
CUORE
988 TeO2 crystals
19 towers
13 floors
52 crystals each
Cryogenic Underground Observatory for Rare Events
80cm
1/10/2008 14IPRD08 - SERGIO DI DOMIZIO
CUORE Sensitivity
mass of lightest neutrino [eV]
m [
eV
]T 1 / 20 2.1⋅1026 y @ 90 C.L.
m 20÷100meV
CUORE
Expected CUORE sensitivityin 5 years
Background 0.01 c/keV/Kg/y
CUORICINO
1/10/2008 15IPRD08 - SERGIO DI DOMIZIO
CUORICINO Background
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
degraded
208Tl60Co
214Bi
1/10/2008 16IPRD08 - SERGIO DI DOMIZIO
Component
< 0.1
< 0.1
Crystal bulk < 0.01
Crystal surface < 0.3
Cu frames bulk < 0.1
Cu frames surface
Neutrons < 0.01
< 0.01
Bkg in DBD region [10-2 c/keV/kg/y]
Environmental Apparatus
~ 2 ÷ 4
Muons
CUORE BackgroundTests 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
Projection to CUORE(goal: 10-2 c/keV/kg/y)
1/10/2008 17IPRD08 - SERGIO DI DOMIZIO
The Three Towers Test
Legnaro Cleaning: TECMTumbling
Electropolishing
Chemical etching
Magnetron sputtering
LNGS CleaningElectropolishingChemical etching
Passivation
Alternative LNGS CleaningElectropolishingChemical etching
PassivationCu frames covered with 50 m PET foil
Test the best Cu cleaning procedure➔Few months data taking, start in Nov 08➔Use CUORICINO cryostat
1/10/2008 18IPRD08 - SERGIO DI DOMIZIO
CUORE Status
● Hut construction started @LNGS
● Crystal production startedFirst batch will arrive in November 08
● Diluition refrigerator is being built
CUORE-0The 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
data taking is foreseen in 2012
CUORE
1/10/2008 19IPRD08 - SERGIO DI DOMIZIO
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 2012