arXiv subjects

L. Pagnanini

Publications and source records attributed to L. Pagnanini.

At least 91 records · Page 5Linked to original sources

arXiv2019

Final result of CUPID-0 phase-I in the search for the $^{82}$Se Neutrinoless Double Beta Decay

CUPID-0 is the first pilot experiment of CUPID, a next-generation project for the measurement of neutrinoless double beta decay (0$ν$DBD) with scintillating bolometers. The detector, consisting of 24 enriched and 2 natural ZnSe crystals, has been taking data at Laboratori Nazionali del Gran Sasso from June 2017 to December 2018, collecting a $^{82}$Se exposure of 5.29 kg$\times$yr. In this paper we present the phase-I results in the search for 0$ν$DBD. We demonstrate that the technology implemented by CUPID-0 allows us to reach the lowest background for calorimetric experiments: $(3.5^{+1.0}_{-0.9})\times10^{-3}$ counts/(keV kg yr). Monitoring 3.88$\times$10$^{25}$ $^{82}$Se nuclei$\times$yr we reach a 90% credible interval median sensitivity of $\rm{T}^{0ν}_{1/2}>5.0\times10^{24} \rm{yr}$ and set the most stringent limit on the half-life of $^{82}$Se 0$ν$DBD : $\rm{T}^{0ν}_{1/2}>3.5\times10^{24} \rm{yr}$ (90% credible interval), corresponding to m$_{ββ} <$ (311-638) meV depending on the nuclear matrix element calculations.

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arXiv2019

Results of CUORE

The Cryogenic Underground Observatory for Rare Events (CUORE) at the Laboratori Nazionali del Gran Sasso, Italy, is the world's largest bolometric experiment. The detector consists of an array of 988 TeO2 crystals, for a total mass of 742 kg. CUORE is presently in data taking, searching for the neutrinoless double beta decay of 130 Te. CUORE is operational since the spring of 2017. The initial science run already allowed to provide the most stringent limit on the neutrinoless double beta decay half-life of 130Te, and to perform the most precise measurement of the two-neutrino double beta decay half-life. Up to date, we have more than doubled the collected exposure. In this talk, we presenteded the most recent results and discuss the present status of the CUORE experiment.

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arXiv2019

Resolution enhancement with light/heat decorrelation in CUPID-0 bolometric detector

The CUPID-0 experiment searches for neutrinoless double beta decay ($0νββ$) using the first array of enriched Zn$^{82}$Se scintillating bolometers with double (heat and light) read-out. To further enhance the CUPID-0 detector performances, the heat-light correlation has been exploited to improve the energy resolution. Different decorrelation algorithms have been studied and the best result is the average reduction of the full width at half maximum (FWHM) energy resolution to $(90.5\pm0.6)~\%$ of its original value , corresponding to a change from $\text{FWHM}=(20.7\pm0.5)~\text{keV}$ to $\text{FWHM}=(18.7\pm0.5)~\text{keV}$ at the 2615 keV $γ$ line.

physics.ins-det↗

arXiv2019

Cryogenic light detectors with enhanced performance for rare events physics

We have developed and tested a new way of coupling bolometric light detectors to scintillating crystal bolometers based upon simply resting the light detector on the crystal surface, held in position only by gravity. This straightforward mounting results in three important improvements: (1) it decreases the amount of non-active materials needed to assemble the detector, (2) it substantially increases the light collection efficiency by minimizing the light losses induced by the mounting structure, and (3) it enhances the thermal signal induced in the light detector thanks to the extremely weak thermal link to the thermal bath. We tested this new technique with a 16 cm$^2$ Ge light detector with thermistor readout sitting on the surface of a large TeO$_2$ bolometer. The light collection efficiency was increased by greater than 50\% compared to previously tested alternative mountings. We obtained a baseline energy resolution on the light detector of 20~eV RMS that, together with increased light collection, enabled us to obtain the best $α$ vs $β/γ$ discrimination ever obtained with massive TeO$_2$ crystals. At the same time we achieved rise and decay times of 0.8 and 1.6 ms, respectively. This superb performance meets all of the requirements for the CUPID (CUORE Upgrade with Particle IDentification) experiment, which is a 1-ton scintillating bolometer follow up to CUORE.

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arXiv2018

Search of the neutrino-less double beta decay of $^{82}$Se into the excited states of $^{82}$Kr with CUPID-0

The CUPID0 experiment searches for double beta decay using cryogenic calorimeters with double (heat and light) read-out. The detector, consisting of 24 ZnSe crystals 95$\%$ enriched in $^{82}$Se and 2 natural ZnSe crystals, started data-taking in 2017 at Laboratori Nazionali del Gran Sasso. We present the search for the neutrino-less double beta decay of $^{82}$Se into the 0$_1^+$, 2$_1^+$ and 2$_2^+$ excited states of $^{82}$Kr with an exposure of 5.74 kg$\cdot$yr (2.24$\times$10$^{25}$ emitters$\cdot$yr). We found no evidence of the decays and set the most stringent limits on the widths of these processes: $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{0_1^+}$)$<$8.55$\times$10$^{-24}$ yr$^{-1}$, $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{2_1^+}$)$<6.25 \times10^{-24}$ yr$^{-1}$, $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{2_2^+}$)$<$8.25$\times$10$^{-24}$ yr$^{-1}$ (90$\%$ credible interval

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arXiv2018

Analysis of cryogenic calorimeters with light and heat read-out for double beta decay searches

The suppression of spurious events in the region of interest for neutrinoless double beta decay will play a major role in next generation experiments. The background of detectors based on the technology of cryogenic calorimeters is expected to be dominated by α particles, that could be disentangled from double beta decay signals by exploiting the difference in the emission of the scintillation light. CUPID-0, an array of enriched Zn$^{82}$Se scintillating calorimeters, is the first large mass demonstrator of this technology. The detector started data-taking in 2017 at the Laboratori Nazionali del Gran Sasso with the aim of proving that dual read-out of light and heat allows for an efficient suppression of the α background. In this paper we describe the software tools we developed for the analysis of scintillating calorimeters and we demonstrate that this technology allows to reach an unprecedented background for cryogenic calorimeters.

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arXiv2018

First Result on the Neutrinoless Double Beta Decay of $^{82}$Se with CUPID-0

We report the result of the search for neutrinoless double beta decay of $^{82}$Se obtained with CUPID-0, the first large array of scintillating Zn$^{82}$Se cryogenic calorimeters implementing particle identification. We observe no signal in a 1.83 kg yr $^{82}$Se exposure and we set the most stringent lower limit on the \onu $^{82}$Se half-life T$^{0ν}_{1/2}>$ 2.4$\times \mathrm{10}^{24}$ yr (90\% credible interval), which corresponds to an effective Majorana neutrino mass m$_{ββ} <$ (376-770) meV depending on the nuclear matrix element calculations. The heat-light readout provides a powerful tool for the rejection of \al\ particles and allows to suppress the background in the region of interest down to (3.6$^{+1.9}_{-1.4}$)$\times$10$^{-3}$\ckky, an unprecedented level for this technique.

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arXiv2018

CUPID-0: the first array of enriched scintillating bolometers for 0νββdecay investigations

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of $^{82}$Se neutrinoless double-beta decay (0$νββ$). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0$νββ$ at the level of 10$^{-3}$ c/keV/kg/y, the lowest value ever measured using cryogenic detectors. This result can be achieved by a state of the art technology for background suppression and thorough protocols and procedures for detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising detector performance which are here preliminarily discussed

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arXiv2018

An innovative technique for the investigation of the 4-fold forbidden beta-decay of $^{50}$V

For the first time a Vanadium-based crystal was operated as cryogenic particle detector. The scintillating low temperature calorimetric technique was used for the characterization of a 22 g YVO$_4$ crystal aiming at the investigation of the 4-fold forbidden non-unique $β^-$ decay of $^{50}$V. The excellent bolometric performance of the compound together with high light output of the crystal makes it an outstanding technique for the study of such elusive rate process. The internal radioactive contaminations of the crystal are also investigated showing that an improvement on the current status of material selection and purification are needed, $^{235/238}$U and $^{232}$Th are measured at the level of 28 mBq/kg, 1.3 Bq/kg and 28 mBq/kg, respectively. In this work, we also discuss a future upgrade of the experimental set-up which may pave the road for the detection of the rare $^{50}$V $β^-$ decay.

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arXiv2017

Results from the first cryogenic NaI detector for the COSINUS project

Recently there is a flourishing and notable interest in the crystalline scintillator material sodium iodide (NaI) as target for direct dark matter searches. This is mainly driven by the long-reigning contradicting situation in the dark matter sector: the positive evidence for the detection of a dark matter modulation signal claimed by the DAMA/LIBRA collaboration is (under so-called standard assumptions) inconsistent with the null-results reported by most of the other direct dark matter experiments. We present the results of a first prototype detector using a new experimental approach in comparison to \textit{conventional} single-channel NaI scintillation light detectors: a NaI crystal operated as a scintillating calorimeter at milli-Kelvin temperatures simultaneously providing a phonon (heat) plus scintillation light signal and particle discrimination on an event-by-event basis. We evaluate energy resolution, energy threshold and further performance parameters of this prototype detector developed within the COSINUS R&D project.

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arXiv2017

Results of the first NaI scintillating calorimeter prototypes by COSINUS

Over almost three decades the TAUP conference has seen a remarkable momentum gain in direct dark matter search. An important accelerator were first indications for a modulating signal rate in the DAMA/NaI experiment reported in 1997. Today the presence of an annual modulation, which matches in period and phase the expectation for dark matter, is supported at > 9$σ$ confidence. The underlying nature of dark matter, however, is still considered an open and fundamental question of particle physics. No other direct dark matter search could confirm the DAMA claim up to now; moreover, numerous null-results are in clear contradiction under so-called standard assumptions for the dark matter halo and the interaction mechanism of dark with ordinary matter. As both bear a dependence on the target material, resolving this controversial situation will convincingly only be possible with an experiment using sodium iodide (NaI) as target. COSINUS aims to even go a step further by combining NaI with a novel detection approach. COSINUS aims to operate NaI as a cryogenic calorimeter reading scintillation light and phonon/heat signal. Two distinct advantages arise from this approach, a substantially lower energy threshold for nuclear recoils and particle identification on an event-by-event basis. These key benefits will allow COSINUS to clarify a possible nuclear recoil origin of the DAMA signal with comparatively little exposure of O(100kg days) and, thereby, answer a long-standing question of particle physics. Today COSINUS is in R&D phase; in this contribution we show results from the 2nd prototype, albeit the first one of the final foreseen detector design. The key finding of this measurement is that pure, undoped NaI is a truly excellent scintillator at low temperatures: We measure 13.1% of the total deposited energy in the NaI crystal in the form of scintillation light (in the light detector).

astro-ph.IM↗

arXiv2017

Development of $^{100}$Mo-containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search

This paper reports on the development of a technology involving $^{100}$Mo-enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ($\sim$1~kg), high optical quality, radiopure $^{100}$Mo-containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2--0.4~kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the $Q$-value of the double-beta transition of $^{100}$Mo (3034~keV) is 4--6~keV FWHM. The rejection of the $α$-induced dominant background above 2.6~MeV is better than 8$σ$. Less than 10~$μ$Bq/kg activity of $^{232}$Th ($^{228}$Th) and $^{226}$Ra in the crystals is ensured by boule recrystallization. The potential of $^{100}$Mo-enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only 10~kg$\times$d exposure: the two neutrino double-beta decay half-life of $^{100}$Mo has been measured with the up-to-date highest accuracy as $T_{1/2}$ = [6.90 $\pm$ 0.15(stat.) $\pm$ 0.37(syst.)] $\times$ 10$^{18}$~yr. Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of $^{100}$Mo.

physics.ins-det↗

arXiv2016

The COSINUS project - a NaI-based cryogenic calorimeter for direct dark matter detection

At present the results in the field of direct dark matter search are in tension: the positive claim of DAMA/LIBRA versus null results from other experiments. However, the comparison of the results of different experiments involves model dependencies, in particular because of the different target materials in use. The COSINUS R&D project aims to operate NaI as a cryogenic calorimeter. Such a detector would not only allow for a direct comparison to DAMA/LIBRA, but would also provide a low(er) nuclear recoil threshold and particle discrimination.

astro-ph.IM↗

arXiv2016

Enriched TeO$_2$ bolometers with active particle discrimination: towards the CUPID experiment

We present the performances of two 92% enriched $^{130}$TeO$_2$ crystals operated as thermal bolometers in view of a next generation experiment to search for neutrinoless double beta decay of $^{130}$Te. The crystals, 435 g each, show an energy resolution, evaluated at the 2615 keV $γ$-line of $^{208}$Tl, of 6.5 and 4.3 keV FWHM. The only observable internal radioactive contamination arises from $^{238}$U (15 and 8 $μ$Bq/kg, respectively). The internal activity of the most problematic nuclei for neutrinoless double beta decay, $^{226}$Ra and $^{228}$Th, are both evaluated as $<$3.1 $μ$Bq/kg for one crystal and $<$2.3 $μ$Bq/kg for the second. Thanks to the readout of the weak Cherenkov light emitted by $β/γ$ particles by means of Neganov-Luke bolometric light detectors we were able to perform an event-by-event identification of $β/γ$ events with a 95% acceptance level, while establishing a rejection factor of 98.21% and 99.99% for $α$ particles.

physics.ins-det↗

arXiv2016

First array of enriched Zn$^{82}$Se bolometers to search for double beta decay

The R&D activity performed during the last years proved the potential of ZnSe scintillating bolometers to the search for neutrino-less double beta decay, motivating the realization of the first large-mass experiment based on this technology: CUPID-0. The isotopic enrichment in $^{82}$Se, the Zn$^{82}$Se crystals growth, as well as the light detectors production have been accomplished, and the experiment is now in construction at Laboratori Nazionali del Gran Sasso (Italy). In this paper we present the results obtained testing the first three Zn$^{82}$Se crystals operated as scintillating bolometers, and we prove that their performance in terms of energy resolution, background rejection capability and intrinsic radio-purity complies with the requirements of CUPID-0.

physics.ins-det↗

arXiv2016

The COSINUS project - perspectives of a NaI scintillating calorimeter for dark matter search

The R&D project COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) aims to develop a cryogenic scintillating calorimeter using NaI as target crystal for direct darkmatter search. Dark matter particles interacting with the detector material generate both a phonon signal and scintillation light. While the phonon signal provides a precise determination of the deposited energy, the simultaneously measured scintillation light allows for a particle identification on an event-by-event basis, a powerful tool to study material-dependent interactions, and to suppress backgrounds. Using the same target material as the DAMA/LIBRA collaboration, the COSINUS technique may offer a unique possibility to investigate and contribute information to the presently controversial situation in the dark matter sector. We report on the dedicated design planned for the NaI proof-of-principle detector and the objectives of using this detection technique in the light of direct dark matter detection.

physics.ins-det↗

arXiv2016

A CsI low temperature detector for dark matter search

Cryogenic detectors have a long history of success in the field of rare event searches. In particular scintillating calorimeters are very suitable detectors for this task since they provide particle discrimination: the simultaneous detection of the thermal and the light signal produced by a particle interaction in scintillating crystals allows to identify the nature of particle, as the light yield depends thereon. We investigate the performance of two large CsI (undoped) crystals ($\sim$122 g each) operated as scintillating calorimeters at milli-Kelvin temperatures in terms of calorimetric properties and background rejection capabilities. Furthermore, we discuss the feasibility of this detection approach towards a background-free future dark matter experiment based on alkali halides crystals, with active particle discrimination via the two-channel detection.

physics.ins-det↗

arXiv2015

CALDER: cryogenic light detector for rare events search

The CALDER project aims at developing cryogenic light detectors with high sensitivity to UV and visible light, to be used for particle tagging in massive bolometers. Indeed the sensitivity of CUORE can be increased by a factor of 3, thanks to the reduction of the $α$-background, obtained by detecting the Cherenkov light (100 eV) emitted by $β/γ$ events. Currently used light detectors have not the features required to address this task, so we decided to develop a new light detector using Kinetic Inductance Detector as a sensor. This approach is very challenging and requires an intensive R$\&$D to be satisfied. The first results of this activity are shown in the following.

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