A
bstract
Neutrinoless double-beta decay is a key process in particle physics. Its experimental investigation is the only viable method that can establish the Majorana nature of neutrinos, providing ...at the same time a sensitive inclusive test of lepton number violation. CROSS (Cryogenic Rare-event Observatory with Surface Sensitivity) aims at developing and testing a new bolometric technology to be applied to future large-scale experiments searching for neutrinoless double-beta decay of the promising nuclei
100
Mo and
130
Te. The limiting factor in large-scale bolometric searches for this rare process is the background induced by surface radioactive contamination, as shown by the results of the CUORE experiment. The basic concept of CROSS consists of rejecting this challenging background component by pulse-shape discrimination, assisted by a proper coating of the faces of the crystal containing the isotope of interest and serving as energy absorber of the bolometric detector. In this paper, we demonstrate that ultra-pure superconductive Al films deposited on the crystal surfaces act successfully as pulse-shape modifiers, both with fast and slow phonon sensors. Rejection factors higher than 99.9% of
α
surface radioactivity have been demonstrated in a series of prototypes based on crystals of Li
2
MoO
4
and TeO
2
. We have also shown that point-like energy depositions can be identified up to a distance of
∼
1 mm from the coated surface. The present program envisions an intermediate experiment to be installed underground in the Canfranc laboratory (Spain) in a CROSS-dedicated facility. This experiment, comprising
∼
3
×
10
25
nuclei of
100
Mo, will be a general test of the CROSS technology as well as a worldwide competitive search for neutrinoless double-beta decay, with sensitivity to the effective Majorana mass down to 70 meV in the most favorable conditions.
The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2 kg array of 20 ...enriched Li2 100MoO4 scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in 100Mo. With more than one year of operation (100Mo exposure of 1.17 kg × yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in 100Mo of T1/2 > 1.5 × 1024 yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨m β β⟩ < (0.31 –0.54 ) eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.
We report the measurement of the two-neutrino double-beta ($2\nu\beta\beta$) decay of $^{100}$Mo to the ground state of $^{100}$Ru using lithium molybdate (\crystal) scintillating bolometers. The ...detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory. From a total exposure of $42.235$ kg$\times$d, the half-life of $^{100}$Mo is determined to be $T_{1/2}^{2\nu}=7.12^{+0.18}_{-0.14}\,\mathrm{(stat.)}\pm0.10\,\mathrm{(syst.)}\times10^{18}$ years. This is the most accurate determination of the $2\nu\beta\beta$ half-life of $^{100}$Mo to date. We also confirm, with the statistical significance of $>3\sigma$, that the single-state dominance model of the $2\nu\beta\beta$ decay of $^{100}$Mo is favored over the high-state dominance model.
CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay (
0
ν
β
β
) of
100
Mo
. In this article, we detail the CUPID-Mo detector concept, assembly and installation in the ...Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20
100
Mo
-enriched 0.2 kg
Li
2
MoO
4
crystals operated as scintillating bolometers at
∼
20
mK
. The
Li
2
MoO
4
crystals are complemented by 20 thin Ge optical bolometers to reject
α
events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of
α
particles at a level much higher than 99.9% – with equally high acceptance for
γ
/
β
events – in the region of interest for
100
Mo
0
ν
β
β
. We present limits on the crystals’ radiopurity:
≤
3
μ
Bq/kg
of
226
Ra
and
≤
2
μ
Bq/kg
of
232
Th
. We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the
100
Mo
0
ν
β
β
decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric
0
ν
β
β
experiment.
Abstract
The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to ...the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li
$$_{2}$$
2
$$^{100}$$
100
MoO
$$_4$$
4
crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of (
$$6.7\pm 0.6$$
6.7
±
0.6
) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of
$$\alpha $$
α
particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this
$$\alpha $$
α
-induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.
Full range resistive thermometers Olivieri, E.; Rotter, M.; De Combarieu, M. ...
Cryogenics (Guildford),
12/2015, Volume:
72, Issue:
Part 2
Journal Article
Peer reviewed
•We present a method to obtain resistive thermometers operating in the 10mK to 300K range.•The thermometer has an electrical resistance adapted to commercial AC resistance bridges.•The thermometer ...has an almost constant, negative, dimensionless sensitivity in the whole 10mK–300K temperature range.•A calibration technique is detailed described to establish the resistance versus temperature curve.•We present time-response and thermal conductance of the a typical full range thermometer.
Resistive thermometers are widely used in low temperature physics, thanks to portability, simplicity of operation and reduced size. The possibility to precisely follow the temperature from room temperature down to the mK region is of major interest for numerous applications, although no single thermometer can nowadays cover this entire temperature range. In this article we report on a method to realize a full range thermometer, capable to measure, by itself, temperatures in the whole above-cited temperature range, with constant sensitivity and sufficient precision for the typical cryogenic applications. We present here the first results for three different full range thermometer prototypes. A detailed description of the set-up used for measurements and characterization is also reported.
Abstract
In the past few years, attention has been drawn to the fact that a precision analysis of two-neutrino double beta decay (2
υββ
) allows the study of interesting physics cases like the ...emission of Majoron bosons and possible Lorentz symmetry violation. These processes modify the summed-energy distribution of the two electrons emitted in 2
υββ
. CUPID is a next-generation experiment aiming to exploit
100
Mo-enriched scintillating Li
2
MoO
4
crystals, operating as cryogenic calorimeters. Given the relatively fast half-life of
100
Mo 2
υββ
and the large exposure that can be reached by CUPID, we expect to measure with very high precision the
100
Mo 2
υββ
spectrum shape, reaching great sensitivities in the search for distortions induced by the physics beyond the Standard Model. In this contribution, we present the CUPID exclusion sensitivity for such New Physics processes, as well as the preliminary projected background of CUPID.
Optimization of a single module of CUPID Ressa, Alberto; Armatol, A.; Armengaud, E. ...
Journal of physics. Conference series,
12/2021, Volume:
2156, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
CUPID is the next generation experiment which will use scintillating cryogenic calorimeters to search for the neutrinoless double β decay. This unobserved process would shed light on the ...nature of the neutrino, which up to our knowledge could be a Majorana or a Dirac particle, and would give us an important hint to explain the lack of antimatter in the universe. This ambitious search needs a detector with unique characteristics such as an extremely low background level and an excellent energy resolution. CUPID is now in advanced R&D state to optimize the detector design in order to completely exploit the potentialities of scintillating cryogenic calorimeters. In the following I will describe the test performed at the LNGS (Laboratori Nazionali del Gran Sasso) of a single module of the future CUPID detector. In this contribution we present the performance obtained with a novel assembly concept, proving that it matches the requirements for CUPID.
Cadmium-116 is one of the favorable candidates for neutrinoless double-beta decay (
0
ν
β
β
) searches from both theoretical and experimental points of view, in particular thanks to the high energy ...of the decay (2813.49 keV), the possibility of the industrial enrichment in
116
Cd
and its use in the well-established production of cadmium tungstate crystal scintillators. In this work, we present low-temperature tests of two
0.6
kg
116
CdWO
4
crystals enriched in
116
Cd
to
82
%
as scintillating bolometers. These detectors were operated underground, with one at the Laboratoire Souterrain de Modane (LSM) in France and the second at the Laboratorio Subterraneo de Canfranc (LSC) in Spain. The two crystals are coupled to bolometric Ge light detectors in order to register the scintillation light. The double readout of heat and scintillation enables reduction in the background in the region of interest by discriminating between different populations of particles. The main goal of these tests is the study of the crystals’ radiopurity and the detectors’ performance. The achieved results are extremely promising, in particular, the detectors demonstrate a high energy resolution (11–16 keV FWHM at 2615 keV) and a high-efficiency discrimination of the alpha background (
∼
20
σ
). These results, achieved for the first time with large mass enriched
116
CdWO
4
crystals, demonstrate prospects of the bolometric technology for high-sensitivity searches of
116
Cd
0
ν
β
β
decay.
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