CUORE, CUORICINO: Results and perspectives

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CUORE, CUORICINO Results and perspectives
Chiara Brofferio
Università di Milano Bicocca and INFN, Sez. di
Milano
On behalf of the CUORICINO and CUORE
Collaborations
Neutrino Telescopes Venice, 22-25 February 2005
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Some basic concepts on bolometers
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The CUORICINO set-up
I run 29 5x5x5 15 3x3x6 TOTAL 130Te MASS
59 moles
II run 40 5x5x5 17 3x3x6 TOTAL 130Te MASS
83 moles
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CUORICINO results (1)
Calibration (U Th) sum spectrum of all the
detectors
The best energy resolution (790 g) _at_ 2615 keV is
3.9 keV
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CUORICINO results (2)
Updated to 6th Dec 04
Background sum spectrum of all the big detectors
in the DBD region
MT 10.8 kg y (big small, natural) BKG 0.18
0.01 counts/ (kev kg y)
FWHM (790g) 7.8 keV (330g) 12.3 keV
T1/20n (130Te) gt 1.8 x 1024 y (90 c.l.)
mee lt 0.2 1.1 eV
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CUORICINO and the NME models
Is CUORICINO able to scrutinize the HM experiment
claim?
mee 50 meV half life for different nuclei and
models 1026 y
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CUORICINO discovery potential
Expected event number in 3 y in a 16 keV energy
window (2 FWHM)
1 s BKG fluctuation (0.18 16 40.7 3)0.5
19
(to be compared with 28.75 events of the HM
claim, with a BKG level which is 0.11 / 0.18
0.6 lower in HM and with an energy resolution
which is 2.5 x better in HM)
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CUORICINO background model (1)
PRELIMINARY !
We have identified 4 possible sources for the
residual BKG in the DBD region

• Neutrons
• 208Tl multi-compton events
• b and a from TeO2 surface
• b and a from Cu (or other mat.) surfaces
• facing the crystals

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CUORICINO background model (2)
Surface contaminations determine peaks at the a
energy, with tails (shape depending on
contamination depth)
In the COINCIDENCE spectrum only CRYSTAL SURFACE
contam. contribute
surface contamination level 1 ng/g vs bulk
c.l. lt 1 (0.1) pg/g for Cu (TeO2)
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CUORE in Gran Sasso Labs
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CUORE detector and shieldings
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The CUORE background
Full Montecarlo simulation on the basis of the
CUORICINO and Mi DBD background analysis
We aim at reaching AT LEAST a reduction by a
factor 10 in Cu surface contamination and by a
factor 4 in TeO2 surface contamination
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Surface Contamination Reduction
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8-detectors Array
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8-detectors vs. Cuoricino
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Development of surface-sensitive bolometers
Use a thin Ge (or TeO2) crystal to make a
composite bolometer
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Development of prototypes
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Preliminary very encouraging results
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CUORE background and sensitivity
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Conclusions

• Cuoricino experiment may confirm the HM claim
  soon, provided the nuclear matrix elements are
  reasonably favourable

• A full Montecarlo simulation for CUORE has been
  developed, on the basis of the CUORICINO and Mi
  DBD background analysis

• A big RD work is going on to reduce the BKG, in
  order to permit to CUORE experiment to
  investigate the inverse hierarchy region of the
  neutrino mass pattern