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E. Previtali

Publications and source records attributed to E. Previtali.

At least 109 records · Page 6Linked to original sources
arXiv2014

Exploring the Neutrinoless Double Beta Decay in the Inverted Neutrino Hierarchy with Bolometric Detectors

Neutrinoless double beta decay (0nubb) is one of the most sensitive probes for physics beyond the Standard Model, providing unique information on the nature of neutrinos. In this paper we review the status and outlook for bolometric 0nubb decay searches. We summarize recent advances in background suppression demonstrated using bolometers with simultaneous readout of heat and light signals. We simulate several configurations of a future CUORE-like bolometer array which would utilize these improvements and present the sensitivity reach of a hypothetical next-generation bolometric 0nubb experiment. We demonstrate that a bolometric experiment with the isotope mass of about 1 ton is capable of reaching the sensitivity to the effective Majorana neutrino mass (|mee|) of order 10-20 meV, thus completely exploring the so-called inverted neutrino mass hierarchy region. We highlight the main challenges and identify priorities for an R&D program addressing them.

nucl-ex↗
arXiv2013

Characterization of bolometric Light Detectors for rare event searches

Bolometers have proven to be very good detectors to search for rare processes thanks to their excellent energy resolution and their low intrinsic background. Further active background rejection can be obtained by the simultaneous readout of the heat and light signals produced by particles interacting in scintillating bolometers, as proposed by the LUCIFER experiment. In this framework, the choice of the light detector and the optimization of its working conditions play a crucial role. In this paper, we report a study of the performances of a Germanium bolometric light detector in terms of signal amplitude, energy resolution and signal time development. The impact of various operational parameters on the detector performances is discussed.

physics.ins-det↗
arXiv2013

The 4 K outer cryostat for the CUORE experiment: construction and quality control

The external shell of the CUORE cryostat is a large cryogen-free system designed to host the dilution refrigerator and the bolometers of the CUORE experiment in a low radioactivity environment. The three vessels that form the outer shell were produced and delivered to the Gran Sasso underground Laboratories in July 2012. In this paper, we describe the production techniques and the validation tests done at the production site in 2012.

physics.ins-det↗
arXiv2013

Performances of a large mass ZnSe bolometer to search for rare events

Scintillating bolometers of ZnSe are the baseline choice of the LUCIFER experiment, whose aim is to observe the neutrinoless double beta decay of 82Se. The independent read-out of the heat and scintillation signals allows to identify and reject alpha particle interactions, the dominant background source for bolometric detectors. In this paper we report the performances of a ZnSe crystal operated within the LUCIFER R&D. We measured the scintillation yield, the energy resolution and the background in the energy region where the signal from neutrinoless double beta decay of 82Se is expected with an exposure of 9.4 kg x days. With a newly developed analysis algorithm we improved the rejection of alpha events, and we estimated the increase in energy resolution obtained by the combination of the heat and light signals. For the first time we measured the light emitted by nuclear recoils, and found it to be compatible with zero. We conclude that the discrimination of nuclear recoils from beta/gamma interactions in the WIMPs energy region is possible, but low-noise light detectors are needed.

physics.ins-det↗
arXiv2013

Search for 14.4 keV solar axions from M1 transition of Fe-57 with CUORE crystals

We report the results of a search for axions from the 14.4 keV M1 transition from Fe-57 in the core of the sun using the axio-electric effect in TeO2 bolometers. The detectors are 5x5x5 cm3 crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg d of data was made using a newly developed low energy trigger which was optimized to reduce the detectors energy threshold. An upper limit of 0.63 c kg-1 d-1 was established at 95% C.L.. From this value, a lower bound at 95% C.L. was placed on the Peccei-Quinn energy scale of fa >= 0.76 10**6 GeV for a value of S=0.55 for the flavor-singlet axial vector matrix element. Bounds are given for the interval 0.15 < S < 0.55.

hep-ex↗
arXiv2013

Validation of techniques to mitigate copper surface contamination in CUORE

In this article we describe the background challenges for the CUORE experiment posed by surface contamination of inert detector materials such as copper, and present three techniques explored to mitigate these backgrounds. Using data from a dedicated test apparatus constructed to validate and compare these techniques we demonstrate that copper surface contamination levels better than 10E-07 - 10E-08 Bq/cm2 are achieved for 238U and 232Th. If these levels are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit on the number of background counts in the region of interest is 0.02-0.03 counts/keV/kg/y depending on the adopted mitigation technique.

nucl-ex↗
arXiv2013

Sensitivity and Discovery Potential of CUORE to Neutrinoless Double-Beta Decay

We present a study of the sensitivity and discovery potential of CUORE, a bolometric double-beta decay experiment under construction at the Laboratori Nazionali del Gran Sasso in Italy. Two approaches to the computation of experimental sensitivity for various background scenarios are presented, and an extension of the sensitivity formulation to the discovery potential case is also discussed. Assuming a background rate of 10^-2 cts/(keV kg y), we find that, after 5 years of live time, CUORE has a 1 sigma sensitivity to the neutrinoless double-beta decay half-life of T_1/2(1 sigma) = 1.6 \times 10^26 y and thus a potential to probe the effective Majorana neutrino mass down to 40-100 meV; the sensitivity at 1.64 sigma, which corresponds to 90% C.L., will be T_1/2(1.64 sigma) = 9.5 \times 10^25 y. This range is compared with the claim of observation of neutrinoless double-beta decay in 76Ge and the preferred range of the neutrino mass parameter space from oscillation results.

nucl-ex↗
arXiv2013

The low energy spectrum of TeO2 bolometers: results and dark matter perspectives for the CUORE-0 and CUORE experiments

We collected 19.4 days of data from four 750 g TeO2 bolometers, and in three of them we were able to set the energy threshold around 3 keV using a new analysis technique. We found a background rate ranging from 25 cpd/keV/kg at 3 keV to 2 cpd/keV/kg at 25 keV, and a peak at 4.7 keV. The origin of this peak is presently unknown, but its presence is confirmed by a reanalysis of 62.7 kg.days of data from the finished CUORICINO experiment. Finally, we report the expected sensitivities of the CUORE0 (52 bolometers) and CUORE (988 bolometers) experiments to a WIMP annual modulation signal.

physics.ins-det↗
arXiv2012

New experimental limits on the alpha decays of lead isotopes

For the first time a PbWO4 crystal was grown using ancient Roman lead and it was run as a cryogenic detector. Thanks to the simultaneous and independent read-out of heat and scintillation light, the detector was able to discriminate beta/gamma interactions with respect to alpha particles down to low energies. New more stringent limits on the alpha decays of the lead isotopes are presented. In particular a limit of T_{1/2} > 1.4*10^20 y at a 90% C.L. was evaluated for the alpha decay of 204Pb to 200Hg.

nucl-ex↗
arXiv2012

Performances of a large mass ZnMoO4 scintillating bolometer for a next generation neutrinoless double beta decay experiment

We present the performances of a 330 g zinc molybdate (ZnMoO4) crystal working as scintillating bolometer as a possible candidate for a next generation experiment to search for neutrinoless double beta decay of 100Mo. The energy resolution, evaluated at the 2615 keV gamma-line of 208Tl, is 6.3 keV FWHM. The internal radioactive contaminations of the ZnMoO4 were evaluated as <6 microBq/kg (228Th) and 27\pm6 microBq/kg (226Ra). We also present the results of the alpha vs beta/gamma discrimination, obtained through the scintillation light as well as through the study of the shape of the thermal signal alone.

nucl-ex↗
arXiv2012

Double-beta decay of $^{130}$Te to the first 0$^{+}$ excited state of $^{130}$Xe with CUORICINO

The CUORICINO experiment was an array of 62 TeO$_{2}$ single-crystal bolometers with a total $^{130}$Te mass of $11.3\,$kg. The experiment finished in 2008 after more than 3 years of active operating time. Searches for both $0ν$ and $2ν$ double-beta decay to the first excited $0^{+}$ state in $^{130}$Xe were performed by studying different coincidence scenarios. The analysis was based on data representing a total exposure of N($^{130}$Te)$\cdot$t=$9.5\times10^{25}\,$y. No evidence for a signal was found. The resulting lower limits on the half lives are $T^{2ν}_{1/2}(^{130} Te\rightarrow^{130} Xe^{*})>1.3\times10^{23}\,$y (90% C.L.), and $T^{0ν}_{1/2}(^{130} Te\rightarrow^{130} Xe^{*})>9.4\times10^{23}\,$y (90% C.L.).

nucl-ex↗
arXiv2011

CUORE crystal validation runs: results on radioactive contamination and extrapolation to CUORE background

The CUORE Crystal Validation Runs (CCVRs) have been carried out since the end of 2008 at the Gran Sasso National Laboratories, in order to test the performances and the radiopurity of the TeO$_2$ crystals produced at SICCAS (Shanghai Institute of Ceramics, Chinese Academy of Sciences) for the CUORE experiment. In this work the results of the first 5 validation runs are presented. Results have been obtained for bulk contaminations and surface contaminations from several nuclides. An extrapolation to the CUORE background has been performed.

nucl-ex↗
arXiv2011

A novel technique of particle identification with bolometric detectors

We report in this paper the proofs that the pulse shape analysis can be used in some bolometers to identify the nature of the interacting particle. Indeed, while detailed analyses of the signal time development in purely thermal detectors have not produced so far interesting results, similar analyses on bolometers built with scintillating crystals seem to show that it is possible to distinguish between an electron or gamma-ray and an alpha particle interaction. This information can be used to eliminate background events from the recorded data in many rare process studies, especially Neutrinoless Double Beta decay search. Results of pulse shape analysis of signals from a number of bolometers with absorbers of different composition (CaMoO4, ZnMoO4, MgMoO4 and ZnSe) are presented and the pulse shape discrimination capability of such detectors is discussed.

nucl-ex↗
arXiv2011

Search for beta plus/EC double beta decay of 120Te

We present a search for beta plus/EC double beta decay of 120Te performed with the CUORICINO experiment, an array of TeO2 cryogenic bolometers. After collecting 0.0573 kg y of 120Te, we see no evidence of a signal and therefore set the following limits on the half-life: T1/2 (0nu) > 1.9 10^{21} y at 90% C.L. for the 0 neutrino mode and T1/2 (2nu) > 7.6 10^{19} y at 90% C.L. for the two neutrino mode. These results improve the existing limits by almost three orders of magnitude (four in the case of 0 neutrino mode).

nucl-ex↗
arXiv2010

130Te Neutrinoless Double-Beta Decay with CUORICINO

We report the final result of the CUORICINO experiment. Operated between 2003 and 2008, with a total exposure of 19.75 kg y of 130Te, CUORICINO was able to set a lower bound on the 130Te 0nDBD half-life of 2.8 10^{24} years at 90% C.L. The limit here reported includes the effects of systematic uncertainties that are examined in detail in the paper. The corresponding upper bound on the neutrino Majorana mass is in the range 300--710 meV, depending on the adopted nuclear matrix element evaluation.

nucl-ex↗
arXiv2010

Muon-induced backgrounds in the CUORICINO experiment

To better understand the contribution of cosmic ray muons to the CUORICINO background, 10 plastic scintillator detectors were installed at the CUORICINO site and operated during the final 3 months of the experiment. From these measurements, an upper limit of 0.0021 counts/(keV kg yr) (95% CL) was obtained on the cosmic ray-induced background in the neutrinoless double beta decay region of interest. The measurements were also compared to Geant4 simulations.

nucl-ex↗