CUORE will be an observatory for rare events consisting of a tightly packed array of TeO 2 bolometers, with a total mass of ∼740 kg, operating in the underground Gran Sasso laboratory. A first step towards CUORE is CUORICINO, a running experiment with 40.7 kg of TeO 2 . Present results from CUORICINO for the neutrinoless double beta decay of 130 Te will be presented here (T 0ν 1/2 ≥1.0×10 24 y, m ν ≤0.26-1.4 eV at 90% C.L.). The status of CUORE preparation and its physics potential, including dark matter searches, will be shown

A De

A Giuliani

A R Smith

B Quiter

C Bucci

C Cosmelli

C Gargiulo

C Rosenfeld

D R Artusa

E B Norman

E E Haller

E Guardincerri

E Longo

E Olivieri

E Pasca

E Previtali

F Bellini

F Ferroni

F T Avignone Iii

G Frossati

G Maier

G Pessina

G Ventura

H A Farach

I Bandac

I G Irastorza

J Beeman

L Risegari

L Torres

M Balata

M Barucci

M Dolinski

M Pallavicini

M Pedretti

M Sisti

N Xu

P Gorla

P Ottonello

R Ardito

R J Creswick

R J Mcdonald

R Maruyama

S Cebrián

S Morganti

S Nisi

S Pirro

S Sangiorgio

S Toffanin

T Gutierrez

V Palmieri

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October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
1
RESULTS FROM CUORICINO AND PROSPECTS FOR
CUORE
S. CEBRIÁN∗, P. GORLA AND I. G. IRASTORZA
Laboratorio de F́ısica Nuclear y Altas Enerǵıas, Universidad de Zaragoza,
E-50009 Zaragoza, Spain
J. BEEMAN, T. GUTIERREZ, R. J. MCDONALD, E. B. NORMAN,
A. R. SMITH AND N. XU
Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA
M. DOLINSKI, E. E. HALLER, R. MARUYAMA AND B. QUITER
University of California, Berkeley, California 94720, USA
A. GIULIANI, M. PEDRETTI AND S. SANGIORGIO
Dipartimento di Fisica e Matemtica dell’Università dell’Insubria e Sezione di
Milano dell’INFN, Como I-22100, Italy
M. BARUCCI, E. OLIVIERI, E. PASCA, L. RISEGARI AND G. VENTURA
Dipartimento di Fisica dell’Università di Firenze e Sezione di Firenze
dell’INFN, Firenze I-50125, Italy
M. BALATA, C. BUCCI AND S. NISI
Laboratori Nazionali del Gran Sasso, I-67010, Assergi (L’Aquila), Italy
V. PALMIERI AND S. TOFFANIN
Laboratori Nazionali di Legnaro, Via Romea 4, I-35020 Legnaro (Padova), Italy
A. DE WAARD AND G. FROSSATI
Kamerling Onnes Laboratory, Leiden University, 2300 RAQ, Leiden, The
Netherlands
C. ARNABOLDI, C. BROFFERIO, S. CAPELLI, F. CAPOZZI,
L. CARBONE, O. CREMONESI, E. FIORINI, A. NUCCIOTTI, M. PAVAN,
October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
G. PESSINA, S. PIRRO, E. PREVITALI, M. SISTI AND L. TORRES
Dipartimento di Fisica dell’Università di Milano-Bicocca e Sezione di Milano
dell’INFN, Milano I-20126, Italy
R. ARDITO AND G. MAIER
Dipartimento di Ingegneria Strutturale del Politecnico di Milano, Milano
I-20133, Italy
E. GUARDINCERRI, P. OTTONELLO AND M. PALLAVICINI
Dipartimento di Fisica dell’Università di Genova e Sezione di Genova
dell’INFN, Genova I-16146, Italy
D. R. ARTUSA, F. T. AVIGNONE III, I. BANDAC, R. J. CRESWICK,
H. A. FARACH AND C. ROSENFELD
Department of Physics and Astronomy, University of South Carolina, Columbia,
South Carolina, USA 29208
F. BELLINI, C. COSMELLI, F. FERRONI, E. LONGO, S. MORGANTI AND
C. GARGIULO
Dipartimento Fisica dell’Università di Roma e Sezione di Roma 1 dell’INFN,
Roma, Italy
CUORE will be an observatory for rare events consisting of a tightly packed array
of TeO2 bolometers, with a total mass of ∼740 kg, operating in the underground
Gran Sasso laboratory. A first step towards CUORE is CUORICINO, a running
experiment with 40.7 kg of TeO2. Present results from CUORICINO for the neu-
trinoless double beta decay of 130Te will be presented here (T0ν
1/2
≥1.0×1024 y,
〈mν〉 ≤0.26-1.4 eV at 90% C.L.). The status of CUORE preparation and its
physics potential, including dark matter searches, will be shown.
1. Introduction
Experiments searching for neutrinoless Double Beta Decay (DBD) can
prove the Majorana character of neutrinos and determine the scale of the
neutrino mass. CUORE (Cryogenic Underground Observatory for Rare
Events)1,2 is a proposed next generation experiment with almost 1000
bolometers of TeO2 and a total mass of ∼740 kg to operate at the Labora-
∗Speaker, fellow at the Dipartimento di Fisica dell’Università di Milano-Bicocca, e-mail:
scebrian@unizar.es
2
October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
3
tori Nazionali del Gran Sasso (LNGS) in Italy. It is intended to investigate
mainly double beta decay but searches for other rare events like the direct
detection of WIMPs are also envisaged3. The first step towards CUORE
is CUORICINO4, running in Gran Sasso since the beginning of 2003 with
40.7 kg of TeO2. In this paper, status and present results for CUORICINO
will be presented and preparation and physics potential for CUORE will
be described.
2. CUORICINO results
The CUORICINO detector consists of a tower of TeO2 crystals with 13
planes (see Fig. 1)4. Eleven of these planes are 4-crystal modules like those
foreseen for CUORE. Two additional planes are made of 9-crystal modules.
CUORICINO contains therefore 44 5×5×5 cm3 crystals (average mass 790
g) and 18 3×3×6 cm3 crystals (average mass 330 g, previously used in the
MiDBD experiment5). The same dilution refrigerator used in MiDBD at
Hall A of LNGS is being used to operate at ∼10 mK.
Figure 1. The CUORICINO detector: scheme of the tower and internal roman lead
shields (left), the 13 planes tower (center), the 4-crystal module (top right) and the
9-crystal module (bottom right).
CUORICINO was cooled for the first time at the beginning of 2003.
Unfortunately during the cooling procedure some of the signal wires discon-
nected so that only 32 of the large crystals and 16 of the small ones could be
October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
4
read. Nevertheless, in April 2003 the first background measurement started
and went on up to October 2003, when data taking was stopped to solve
the wiring problem. CUORICINO was cooled again in March 2004, losing
only two of the electrical contacts this time. Data taking was resumed and
is progressing.
Up to June 2004, the total collected statistics are of 52785 h×crystal for
the 5×5×5 cm3 detectors and 14115 h×crystal for the 3×3×6 cm3 ones.
Preliminary analysis indicates that ∼70% of the events in the neutrinoles
DBD region can be due to surface contaminations on crystals and copper
detector holders. By comparing Monte Carlo simulations with measured
data in CUORICINO it has been deduced that the shapes and rates of the
observed degraded alpha peaks are well reproduced assuming surface con-
taminations on the crystals and copper supporters having a density profile
decaying exponentially with constants between 0.1 and 10 µm and being
from 2 to 3 orders of magnitude greater than the bulk contaminations6.
The present background in the neutrinoless DBD region is 0.17±0.04
c/keV/kg/y. Since no peak appears in the anticoincidence background spec-
trum at the DBD transition energy (2529 keV) a 90% C.L. lower limit on
the 130Te ββ(0ν) half-life of 1.0 × 1024 years has been derived. The corre-
sponding constraint on the effective neutrino mass ranges from 0.26 to 1.4
eV according to the various evaluations of nuclear matrix elements.
3. Prospects for CUORE
CUORE1,2,3 will be a high granularity detector consisting of an array of
19 towers, containing each 13 CUORICINO-like modules (with 4 5x5x5
cm3 TeO2 crystals). The total mass will be of ∼740 kg. A new dilution
refrigerator is being built to operate at ∼10 mK.
The surface contaminations on crystals and copper holders detected
in CUORICINO are a serious problem for the CUORE sensitivity; differ-
ent R&D works are being devoted to solve it. A direct measurement of
the 238U and 232Th surface contaminations on copper attacking samples
with acid during different times and analyzing the obtained solutions with
ICPMS (Inductive Coupled Plasma Mass Spectroscopy) is being attempted.
A preliminary result for a sample of the CUORICINO copper shows that
the contamination quickly decreases with depth, in good agreement with
our background model. If the elimination of the surface contaminations
was not possible, an active rejection of surface events could be the solu-
tion. This technique has been proved using composite bolometers made
October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
5
covering the TeO2 crystal with very thin Ge/Si detectors; pulse amplitudes
from the Ge/Si thermistor are much higher for surface events allowing their
identification7.
The sensitivity of CUORE will strongly depend on the final background
levels achieved. CUORE background predictions are based on Monte Carlo
simulations and data from CUORICINO (see the CUORE Proposal1). As-
suming for surface contaminations a reduction of a factor of 10 with respect
to CUORICINO, the CUORE background could be of ∼0.007 c/keV/kg/y
in the neutrinoless DBD region and of ∼0.05 c/keV/kg/d near the thresh-
old.
The physics potential of CUORE has been studied in detail in Ref.3.
Regarding the search for neutrinoless DBD of 130Te, assuming five years
of data, in a conservative (optimistic) situation with background b=0.01
(0.001) c/keV/kg/y and energy resolution Γ=10 (5) keV, the expected sen-
sitivity is of 1.5 (6.5) ×1026 y for the half-life. The corresponding regions
explored for the neutrino effective mass are 23-118 (11-57) meV, depending
on the nuclear matrix elements considered.
Figure 2 shows the expected exclusion plots for the direct detection of
WIMPs calculated assuming an energy threshold of 10 keV, an exposure of
one year and two different background levels in the low energy region, 0.05
and 0.01 c/keV/kg/d3. As a reference, the limit obtained in the previous
MiDBD experiment is also shown8.
Since CUORE will be a very massive experiment, a search for the annual
modulation in the WIMP signal might be possible provided a good stability
was achieved. Following the method from Ref.9, the sensitivity of CUORE
has been evaluated in Fig. 3 assuming an energy threshold of 10 keV, an
exposure of two years and background levels of 0.05 and 0.01 c/keV/kg/d.
The more optimistic case of a 5 keV threshold with the lowest background
has been also plotted. The regions of WIMPs above the curves would give
a positive annual modulation signal at 90% C.L. with a 50% probability.
Acknowledgments
One of us (S. Cebrián) greatly acknowledges Spanish foundation “Fun-
dación Areces” for the support of a fellowship.
References
1. CUORE Proposal, January 2004, http://crio.mib.infn.it/wig.
2. C. Arnaboldi et al., Nucl. Instrum. Meth. A518, 775 (2004).
October 15, 2004 19:5 Proceedings Trim Size: 9in x 6in idm
6
1 5 10 50 100 5001000
MW
 
GeV 
10 12
10 10
10 8
10 6
10 4
 n 
nrabn

 
Figure 2. Expected exclusion plots for WIMP direct detection in CUORE (solid lines)
and MiDBD result (dashed line). See text for details.
1 5 10 50 100 5001000
MW
 
GeV 
10 11
10 10
10 9
10 8
10 7
10 6
 n 
nrabn

 
Figure 3. Sensitivity plots for the annual modulation effect in the WIMP signal for
CUORE with threshold of 10 keV (thick solid lines) and 5 keV (dashed line). See text
for details.
3. C. Arnaboldi et al., Astrop. Phys. 20, 91 (2003).
4. C. Arnaboldi et al., Phys. Lett. B584, 260 (2004).
5. C. Arnaboldi et al., Phys.Lett. B557, 167 (2003).
6. S. Capelli, Poster Session at Neutrino 2004, Paris, June 2004. To appear in
Nucl. Phys. B (Proc. Suppl.).
7. M. Pedretti, Poster Session at Neutrino 2004, Paris, June 2004. To appear in
Nucl. Phys. B (Proc. Suppl.).
8. A. Giuliani et al., Nucl. Phys. (Proc. Suppl.) B110, 64 (2002).
9. S. Cebrián et al., Astrop. Phys. 14, 339 (2001).


RESULTS FROM CUORICINO AND PROSPECTS FOR CUORE

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RESULTS FROM CUORICINO AND PROSPECTS FOR CUORE

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