Explore the vast range of titles available.

In this paper we present the first measurement of a Gallium Arsenide (GaAs) crystal as a scintillating calorimeter with dual heat and light readout within the DAREDEVIL project. The experimental setup features a 4.3 g GaAs ( GaAs-1) crystal, operated at approximately 10 mK coupled with a Neutron Transmutation Doped (NTD) thermal sensor for phonon detection and an auxiliary calorimeter for the detection of scintillation light. For the GaAs-1 crystal, a baseline resolution of 121 ± 2 eV has been achieved. While, with a 3.5 g GaAs (GaAs-2) crystal an even better baseline resolution of 44.5 ± 0.8 eV was achieved. Alpha and X-ray calibration sources were used to study the scintillation light response to different types of interacting radiation. The GaAs crystal exhibits a strong particle discrimination capability based on the emitted scintillation light, featuring a light yield (LY) of 0.9 ± 0.2 keV/MeV for α induced events and 0.07 ± 0.01 keV/MeV for β / γ events, both measured at 1 MeV. The unusual luminescence behavior, i.e. more light being produced under irradiation by α particles warrants further investigation, particularly due to its potential to enhance sensitivity to low-energy nuclear recoils from light dark matter scattering.

In the quest for direct dark matter detection, innovative approaches to lower the detection threshold and explore the sub-GeV mass range, have gained high relevance in the last decade. This study presents the pioneering use of Gallium Arsenide (GaAs) as a low-temperature calorimeter for probing dark matter-electron interactions within the DAREDEVIL (DARk-mattEr DEVIces for Low energy detection) project. Our experimental setup features a GaAs crystal at an ultralow temperature of 15 mK, coupled with a Neutron Transmutation Doped Germanium (NTD-Ge) thermal sensor for precise energy estimation. This configuration is the first step towards detecting single electrons scattered by dark matter particles within the GaAs crystal, to improve the sensitivity to low-mass dark matter candidates significantly. Taking advantage of the production of optical phonons in polar materials such as GaAs gives the possibility to study the scattering of sub-MeV dark matter. This paper presents a detailed analysis of the detector’s response, using a calibration spectrum using α particles and X-ray events. While the results do not meet the ambitious eV scale threshold yet, they establish a solid benchmark for assessing the detector’s current performance and sensitivity. This work not only highlights the detector’s potential but also sets the stage for future enhancements aimed at achieving the eV threshold, underscoring the promising direction of this detector technology. These findings demonstrate the feasibility of using GaAs as a cryogenic calorimeter and hence open new avenues for investigating the elusive nature of dark matter through innovative direct detection techniques.

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.

Highly forbidden β decays provide a sensitive test to nuclear models in a regime in which the decay goes through high spin-multipole states, similar to the neutrinoless double- β decay process. There are only 3 nuclei ( 50 V, 113 Cd, 115 In) which undergo a 4 th forbidden non-unique β decay. In this work, we compare the experimental 113 Cd spectrum to theoretical spectral shapes in the framework of the spectrum-shape method. We measured with high precision, with the lowest energy threshold and the best energy resolution ever, the β spectrum of 113 Cd embedded in a 0.43 kg CdWO 4 crystal, operated over 26 days as a bolometer at low temperature in the Canfranc underground laboratory (Spain). We performed a Bayesian fit of the experimental data to three nuclear models (IBFM-2, MQPM and NSM) allowing the reconstruction of the spectral shape as well as the half-life. The fit has two free parameters, one of which is the effective weak axial-vector coupling constant, g A eff , which resulted in g A eff between 1.0 and 1.2, compatible with a possible quenching. Based on the fit, we measured the half-life of the 113 Cd β decay including systematic uncertainties as 7 . 73 - 0.57 + 0.60 × 10 15 yr, in agreement with the previous experiments. These results represent a significant step towards a better understanding of low-energy nuclear processes.

The ACCESS (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes) project aims to establish a novel technique to perform precision measurements of forbidden β -decays, which can serve as an important benchmark for nuclear physics calculations and represent a significant background in astroparticle physics experiments. ACCESS will operate a pilot array of cryogenic calorimeters based on natural and doped crystals containing β -emitting radionuclides. In this way, natural (e.g. 113 Cd and 115 In) and synthetic isotopes (e.g. 99 Tc) will be simultaneously measured with a common experimental technique. The array will also include further crystals optimised to disentangle the different background sources, thus reducing the systematic uncertainty. In this paper, we give an overview of the ACCESS research program, discussing a detector design study and promising results of 115 In.

RES-NOVA is a newly proposed experiment for detecting neutrinos from astrophysical sources, mainly Supernovae, using an array of cryogenic detectors made of PbWO4 crystals produced from archaeological Pb. This unconventional material, characterized by intrinsic high radiopurity, enables low-background levels in the region of interest for the neutrino detection via Coherent Elastic neutrino-Nucleus Scattering (CEνNS). This signal lies at the detector energy threshold, O(1 keV), and it is expected to be hidden by naturally occurring radioactive contaminants of the crystal absorber. Here, we present the results of a radiopurity assay on a 0.84 kg PbWO4 crystal produced from archaeological Pb operated as a cryogenic detector. The crystal internal radioactive contaminations are: 232Th <40 μBq/kg, 238U <30 μBq/kg, 226Ra 1.3 mBq/kg and 210Pb 22.5 mBq/kg. We also present a background projection for the final experiment and possible mitigation strategies for further background suppression. The achieved results demonstrate the feasibility of realizing this new class of detectors.

Vibrations from experimental setups and the environment are a persistent source of noise for low-temperature calorimeters searching for rare events, including neutrinoless double beta (0 ν β β ) decay or dark matter interactions. Such noise can significantly limit experimental sensitivity to the physics case under investigation. Here, we report the detection of marine microseismic vibrations using mK-scale calorimeters. This study employs a multi-device analysis correlating data from CUORE, the leading experiment in the search for 0 ν β β decay with mK-scale calorimeters, and the Copernicus Earth Observation program, revealing the seasonal impact of Mediterranean Sea activity on CUORE’s energy thresholds, resolution, and sensitivity over four years. The detection of marine microseisms underscores the need to address faint environmental noise in ultra-sensitive experiments. Understanding how such noise couples to the detector and developing mitigation strategies is essential for next-generation experiments. We demonstrate one such strategy: a noise decorrelation algorithm implemented in CUORE using auxiliary sensors, which reduces vibrational noise and improves detector performance. Enhancing sensitivity to 0 ν β β decay and to rare events with low-energy signatures requires identifying unresolved noise sources, advancing noise reduction methods, and improving vibration suppression systems, all of which inform the design of next-generation rare event experiments. Low-temperature calorimeters used in rare-event searches are often limited in sensitivity by noise, especially at low energies. Here, the authors show that CUORE can detect microseismic vibrations from the Mediterranean Sea and that a denoising algorithm reduces this noise, improving detector resolution and rare-event sensitivity.

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.

A wide range of scintillating bolometers are under investigation for applications in the search for rare events and processes beyond the Standard Model. In this work, we report the first measurement of a natural, non-molybdenum-doped, lithium tungstate (Li 2 WO 4 ) crystal operated underground as a scintillating cryogenic calorimeter. The detector achieved a baseline energy resolution of 0.5 keV RMS with a low-energy threshold of about 1.5 keV. The simultaneous readout of heat and light enabled particle identification, revealing a clear separation between β / γ , α , and nuclear recoil populations above 300 keV, with a light-yield-based particle discrimination better than 6 σ . These results, fully comparable with those achieved with other compounds in the field, demonstrate that Li 2 WO 4 is a promising candidate for rare-event searches. In particular, the combination of excellent radio-purity (with U/Th levels below 0.5 mBq/kg) and sensitivity to neutron interactions via the 6 Li(n, α ) 3 H reaction makes this material an attractive option for next-generation experiments in dark matter, coherent elastic neutrino-nucleus scattering, and spin-dependent interactions.

The CUPID-Mo experiment to search for 0νββ decay in 100Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0νββ decay experiment. CUPID-Mo was comprised of 20 enriched Li2100MoO4 scintillating calorimeters, each with a mass of ∼0.2 kg, operated at ∼20 mK. We present here the final analysis with the full exposure of CUPID-Mo (100Mo exposure of 1.47 kg×year) used to search for lepton number violation via 0νββ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the 100Mo 0νββ decay half-life of T1/20ν>1.8×1024 year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of mββ <(0.28-0.49) eV, dependent upon the nuclear matrix element utilized.