11 research outputs found
Recent progress in oxide scintillation crystals development by low-thermal gradient Czochralski technique for particle physics experiments
No full textInternational audienceModern particle physics experiments call for high performance scintillation detectors with unique properties: radiation-resistant in high energy and astrophysics, highly radiopure, containing certain elements or enriched isotopes in astroparticle physics. The low-thermal gradient Czochralski (LTG CZ) crystal growth technique provides excellent quality large volume radiopure crystal scintillators. Absence of thermoelastic stress in the crystal and overheating of the melt in the LTG CZ method is particularly significant in production of crystalline materials with strong thermal anisotropic properties and low mechanical strength, with a very high yield of crystalline boules and low losses of initial charge, crucially important in production of crystal scintillators from enriched isotopes for double beta decay experiments. Here we discuss progress in development of the well known scintillators (Bi(4)Ge(3)O(12) (BGO), CdWO(4), ZnWO(4), CaMoO(4), PbMoO(4)), as well as R{&}D of new materials (ZnMoO(4), Li(2)MoO(4), Na(2)Mo(2)O(7)) for the next generation experiments in particle physics
Study of Dark Matter with directionality approach using ZnWO
No full textLow-background anisotropic scintillators represents an innovative approach to study the presence, in the galactic halo, of those Dark Matter (DM) candidate particles able to induce just nuclear recoils, by exploiting the directionality approach. ZnWO4 crystal scintillators are particularly well-suited for such investigations, since the light output and scintillation pulse shape vary depending on the angle of incidence of heavy particles (e.g., α particles and nuclear recoils) relative to the crystal axes. Due to this anisotropic behavior, a signal induced by those DM candidates can be investigated in two independent modes: studying the directionality variation both of the signal rate and of the pulse shape discrimination from the γ/β radiation (that does not give rise to any anisotropic effects). Additionally, the detector’s sensitivity spans a wide range of DM masses, attributed to the differing atomic masses of its target nuclei (Zn, W, and O). Building on these characteristics, the ADAMO project carried out new studies to examine the anisotropic response of ZnWO4 scintillators to α particles and nuclear recoils induced by neutron scattering. A summary of these investigations are presented in this paper
New measurement of double beta decays of Mo to excited states of Ru with the CUPID-Mo experiment
No full textInternational audienceThe CUPID-Mo experiment, located at Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20 LiMoO (LMO) calorimeters each equipped with a Ge light detector (LD) for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double beta decays of Mo to the first 0 and excited states of Ru using the full CUPID-Mo exposure (2.71 kgyr of LMO). We measure the half-life of decay to the state as . The bolometric technique enables measurement of the electron energies as well as the gamma rays from nuclear de-excitation and this allows us to set new limits on the two-neutrino decay to the state of T^{2\nu \rightarrow 2_1^+}_{1/2}>4.4\times 10^{21} \ \mathrm{yr} \ \text{(90 % c.i.)} and on the neutrinoless modes of T_{1/2}^{0\nu\rightarrow 2_1^+}>2.1\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}, T_{1/2}^{0\nu\rightarrow 0_1^+}>1.2\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}. Information on the electrons spectral shape is obtained which allows us to make the first comparison of the single state (SSD) and higher state (HSD) decay models for the excited state of Ru
Probing Beyond the Standard Model physics using the improved description of Mo decay spectral shape with CUPID-Mo
No full textInternational audienceThe current experiments searching for neutrinoless double- () decay also collect large statistics of Standard Model allowed two-neutrino double- () decay events. These can be used to search for Beyond Standard Model (BSM) physics via decay spectral distortions. Mo has a natural advantage due to its relatively short half-life, allowing higher decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a Mo exposure of 1.47 kg y, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on decays with the emission of one or more Majorons, on decay with Lorentz violation, and decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of decay events among the next-generation experiments
Li<sub>2</sub><sup>100depl</sup>MoO<sub>4</sub> Scintillating Bolometers for Rare-Event Search Experiments
No full textWe report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-β active isotope 100Mo (Li2100deplMoO4). We used two Li2100deplMoO4 cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double-β search experiments with 100Mo-enriched Li2MoO4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li2100deplMoO4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li2100deplMoO4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV γs), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity (228Th and 226Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li2MoO4 using natural or 100Mo-enriched molybdenum content. The prospects of Li2100deplMoO4 bolometers for use in rare-event search experiments are briefly discussed
The background model of the CUPID-Mo experiment
No full textCUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a
demonstrator for the next generation decay experiment, CUPID.
It consisted of an array of 20 enriched LiMoO bolometers and
20 Ge light detectors and has demonstrated that the technology of scintillating
bolometers with particle identification capabilities is mature. Furthermore,
CUPID-Mo can inform and validate the background prediction for CUPID. In this
paper, we present a detailed model of the CUPID-Mo backgrounds. This model is
able to describe well the features of the experimental data and enables studies
of the decay and other processes with high precision. We also
measure the radio-purity of the LiMoO crystals which are
found to be sufficient for the CUPID goals. Finally, we also obtain a
background index in the region of interest of
3.7(stat)(syst)counts/E/mol/yr,
the lowest in a bolometric decay experiment
Measurement of the decay rate and spectral shape of Mo from the CUPID-Mo experiment
No full textInternational audienceNeutrinoless double beta decay () is a yet unobserved nuclear process which would demonstrate Lepton Number violation, a clear evidence of beyond Standard Model physics. The process two neutrino double beta decay ( is allowed by the Standard Model and has been measured in numerous experiments. In this letter, we report a measurement of decay half-life of Mo to the ground state of Ru of ~yr by the CUPID-Mo experiment. With a relative precision of % this is the most precise measurement to date of a decay rate in Mo. In addition, we constrain higher-order corrections to the spectral shape which provides complementary nuclear structure information. We report a novel measurement of the shape factor , which is compared to theoretical predictions for different nuclear models. We also extract the first value for the effective axial vector coupling constant obtained from a spectral shape study of decay
Pulse Shape Discrimination in CUPID-Mo using Principal Component Analysis
No full textInternational audienceCUPID-Mo is a cryogenic detector array designed to search for neutrinoless double-beta decay (0νββ) of 100Mo. It uses 20 scintillating 100Mo-enriched Li2MoO4 bolometers instrumented with Ge light detectors to perform active suppression of α backgrounds, drastically reducing the expected background in the 0νββ signal region. As a result, pileup events and small detector instabilities that mimic normal signals become non-negligible potential backgrounds. These types of events can in principle be eliminated based on their signal shapes, which are different from those of regular bolometric pulses. We show that a purely data-driven principal component analysis based approach is able to filter out these anomalous events, without the aid of detector response simulations
The CUPID-Mo experiment for neutrinoless double-beta decay: performance and prospects
No full textInternational audienceCUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay () of . 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 -enriched 0.2 kg crystals operated as scintillating bolometers at . The crystals are complemented by 20 thin Ge optical bolometers to reject 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 particles at a level much higher than 99.9% – with equally high acceptance for / events – in the region of interest for . We present limits on the crystals’ radiopurity: of and of . We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the 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 experiment
