Search for: All records

Cryogenic calorimetric experiments to search for neutrinoless double-beta decay (0νββ) are highly competitive, scalable, and versatile in isotope choice. The largest planned detector array, CUPID, consists of about 1500 individual Li₂¹⁰⁰MoO₄ detector modules, with further scaling envisioned for a follow-up experiment (CUPID-1T). In this article, we present a novel detector concept targeting this second stage, using a low-impedance TES-based readout for the Li₂MoO₄ absorber. This design is easily mass-produced and supports multiplexed readout. We describe the detector design and results from a first prototype operated at the NEXUS shallow underground facility at Fermilab. The detector is a 2-cm-side cube with a mass of 21 g, strongly thermally coupled to its readout chip, allowing rise-times of approximately 0.5 ms. This is more than an order of magnitude faster than current NTD-based detectors and is expected to effectively mitigate backgrounds caused by pile-up of two independent two-neutrino decay events occurring close in time. With a baseline resolution of 1.95 keV (FWHM), these performance parameters extrapolate to a background index from pile-up as low as 5 × 10⁻⁶ counts/keV/kg/year in CUPID-sized crystals. The detector was calibrated up to the MeV region, demonstrating sufficient dynamic range for 0νββ searches. In combination with a SuperCDMS HVeV detector, this setup also enabled a precision measurement of the scintillation time constants of Li₂MoO₄, revealing a primary component with a fast ~20 μs time scale. 

Various dark matter search experiments employ phonon-based crystal detectors operated at cryogenic temperatures. Some of these detectors, including certain silicon detectors used by the SuperCDMS Collaboration, are able to achieve single-charge sensitivity when a voltage bias is applied across the detector. The total amount of phonon energy measured by such a detector is proportional to the number of electron-hole pairs created by the interaction. However, crystal impurities and surface effects can cause propagating charges to either become trapped inside the crystal or create additional unpaired charges, producing nonquantized measured energy as a result. A new analytical model for describing these detector response effects in phonon-based crystal detectors is presented. This model improves upon previous versions by demonstrating how the detector response, and thus the measured energy spectrum, is expected to differ depending on the source of events. We use this model to extract detector response parameters for SuperCDMS HVeV detectors, and illustrate how this robust modeling can help statistically discriminate between sources of events in order to improve the sensitivity of dark matter search experiments. 

Abstract CUPID is a next-generation bolometric experiment to search for neutrinoless double-beta decay ($$0\nu \beta \beta $$ $0\nu \beta \beta$ ) of¹⁰⁰Mo using Li$$_2$$ $_2^{}$ MoO$$_4$$ $_4^{}$ scintillating crystals. It will operate 1596 crystals at$$\sim $$ $\sim$ 10 mK in the CUORE cryostat at the Laboratori Nazionali del Gran Sasso in Italy. Each crystal will be facing two Ge-based bolometric light detectors for$$\alpha $$ $\alpha$ rejection. We compute the discovery and the exclusion sensitivity of CUPID to$$0\nu \beta \beta $$ $0\nu \beta \beta$ in a Frequentist and a Bayesian framework. This computation is done numerically based on pseudo-experiments. For the CUPIDbaselinescenario, with a background and an energy resolution of$$1.0 \times 10^{-4}$$ $1.0\times {10}^{-4}$ counts/keV/kg/yr and 5 keV FWHM at the Q-value, respectively, this results in a Bayesian exclusion sensitivity (90% c.i.) of$$\hat{T}_{1/2} > 1.6 \times 10^{27} \ \textrm{yr}$$ ${\hat{T}}_{1/2}>1.6\times {10}^{27}\text{yr}$ , corresponding to the effective Majorana neutrino mass of$$\hat{m}_{\beta \beta } < \ 9.6$$ ${\hat{m}}_{\beta \beta }<9.6$ –$$28 \ \textrm{meV}$$ $28\text{meV}$ . The Frequentist discovery sensitivity (3$$\sigma $$ $\sigma$ ) is$$\hat{T}_{1/2}= 1.0 \times 10^{27} \ \textrm{yr}$$ ${\hat{T}}_{1/2}=1.0\times {10}^{27}\text{yr}$ , corresponding to$$\hat{m}_{\beta \beta }= \ 12$$ ${\hat{m}}_{\beta \beta }=12$ –$$36 \ \textrm{meV}$$ $36\text{meV}$ . 

The experiment aims to measure the coherent elastic neutrino-nucleus scattering process from antineutrinos emitted by a research nuclear reactor operated by the Institut Laue-Langevin (Grenoble, France). This article presents a description of the experimental installation and the detector performance achieved during its commissioning with a mini-CryoCube module consisting of three 42-g germanium cryogenic calorimeters. The baseline resolutions and background levels are reported both during reactor-on and reactor-off periods and as noise mitigation techniques were improved. A baseline resolution of 40 eV electron equivalent was achieved for the ionization channel after setup improvements, and the phonon channel resolutions ranged from 50 to 80 eV of total phonon energy. In the energy region from 2 to 7 keV, a nuclear recoil rate of $14\left(3\right)\mathrm{events}/\left(\mathrm{kg}\mathrm{day}\mathrm{keV}\right)$ is measured during the reactor-off period selecting events in coincidence with muon veto signals. This rate is in agreement with the cosmogenic neutron rate calculated from GEANT4 simulations. After the rejection of events in coincidence with signals in the muon veto detectors, a combined 90% confidence level limit on the nuclear recoil background of $<9\mathrm{events}/\left(\mathrm{kg}\mathrm{day}\mathrm{keV}\right)$ is obtained in that energy region during the reactor-on period, which is compatible with our GEANT4 model calculation corresponding to a total rate of $5\mathrm{events}/\left(\mathrm{kg}\mathrm{day}\mathrm{keV}\right)$ . The sensitivity of this analysis was however found to be limited by a surface event contamination which is currently being addressed by the Collaboration with upgraded detectors. 

We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used in all previous HVeV studies. A blind analysis of $6.1\mathrm{g}·\mathrm{days}$ of exposure produces exclusion limits for dark matter-electron scattering cross sections for masses as low as $1\mathrm{MeV}/c^2$ , as well as on the photon-dark photon mixing parameter and the coupling constant between axionlike particles and electrons for particles with masses $>1.2\mathrm{eV}/c^2$ probed via absorption processes.