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1. Scintillating Bubble Chambers for Rare Event Searches

   https://doi.org/10.3390/universe9080346  

   Alfonso-Pita, Ernesto ; Behnke, Edward ; Bressler, Matthew ; Broerman, Benjamin ; Clark, Kenneth ; Corbett, Jonathan ; Dahl, C. Eric ; Dering, Koby ; de St. Croix, Austin ; Durnford, Daniel ; et al ( August 2023 , Universe)

   Baracchini, Elisabetta (Ed.)

   The Scintillating Bubble Chamber (SBC) collaboration is developing liquid-noble bubble chambers for the detection of sub-keV nuclear recoils. These detectors benefit from the electron recoil rejection inherent in moderately-superheated bubble chambers with the addition of energy reconstruction provided from the scintillation signal. The ability to measure low-energy nuclear recoils allows the search for GeV-scale dark matter and the measurement of coherent elastic neutrino-nucleus scattering on argon from MeV-scale reactor antineutrinos. The first physics-scale detector, SBC-LAr10, is in the commissioning phase at Fermilab, where extensive engineering and calibration studies will be performed. In parallel, a functionally identical low-background version, SBC-SNOLAB, is being built for a dark matter search underground at SNOLAB. SBC-SNOLAB, with a 10 kg-yr exposure, will have sensitivity to a dark matter–nucleon cross section of 2×10−42 cm2 at 1 GeV/c2 dark matter mass, and future detectors could reach the boundary of the argon neutrino fog with a tonne-yr exposure. In addition, the deployment of an SBC detector at a nuclear reactor could enable neutrino physics investigations including measurements of the weak mixing angle and searches for sterile neutrinos, the neutrino magnetic moment, and the light Z’ gauge boson.

    

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2. Calibration of the liquid argon ionization response to low energy electronic and nuclear recoils with DarkSide-50

   The DarkSide collaboration) Agnes, P. ; Albuquerque, I. F. ; Alexander, T. ; Alton, A. K. ; Ave, M. ; Back, H. O. ; Batignani, G. ; Biery, K. ; Bocci, V. ; Bonivento, W. M. ; et al ( July 2021 , ArXivorg)

   null (Ed.)

   DarkSide-50 has demonstrated the high potential of dual-phase liquid argon time projection chambers in exploring interactions of WIMPs in the GeV/c2 mass range. The technique, based on the detection of the ionization signal amplified via electroluminescence in the gas phase, allows to explore recoil energies down to the sub-keV range. We report here on the DarkSide-50 measurement of the ionization yield of electronic recoils down to about 180 eVer, exploiting 37Ar and 39Ar decays, and extrapolated to a few ionization electrons with the Thomas-Imel box model. Moreover, we present the determination of the ionization response to nuclear recoils down to ∼ 500 eVnr , the lowest ever achieved in liquid argon, using in situ neutron calibration sources and external datasets from neutron beam experiments. 

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3. Performance of the ReD TPC, a novel double-phase LAr detector with silicon photomultiplier readout

   https://doi.org/10.1140/epjc/s10052-021-09801-6  

   Agnes, P. ; Albergo, S. ; Albuquerque, I. ; Arba, M. ; Ave, M. ; Boiano, A. ; Bonivento, W. M. ; Bottino, B. ; Bussino, S. ; Cadeddu, M. ; et al ( November 2021 , The European Physical Journal C)

   Abstract A double-phase argon Time Projection Chamber (TPC), with an active mass of 185 g, has been designed and constructed for the Recoil Directionality (ReD) experiment. The aim of the ReD project is to investigate the directional sensitivity of argon-based TPCs via columnar recombination to nuclear recoils in the energy range of interest (20– $$200\,\hbox {keV}_{nr}$$ 200 keV nr ) for direct dark matter searches. The key novel feature of the ReD TPC is a readout system based on cryogenic Silicon Photomultipliers (SiPMs), which are employed and operated continuously for the first time in an argon TPC. Over the course of 6 months, the ReD TPC was commissioned and characterised under various operating conditions using $$\gamma $$ γ -ray and neutron sources, demonstrating remarkable stability of the optical sensors and reproducibility of the results. The scintillation gain and ionisation amplification of the TPC were measured to be $$g_1 = (0.194 \pm 0.013)$$ g 1 = ( 0.194 ± 0.013 ) photoelectrons/photon and $$g_2 = (20.0 \pm 0.9)$$ g 2 = ( 20.0 ± 0.9 ) photoelectrons/electron, respectively. The ratio of the ionisation to scintillation signals (S2/S1), instrumental for the positive identification of a candidate directional signal induced by WIMPs, has been investigated for both nuclear and electron recoils. At a drift field of 183 V/cm, an S2/S1 dispersion of 12% was measured for nuclear recoils of approximately 60– $$90\,\hbox {keV}_{nr}$$ 90 keV nr , as compared to 18% for electron recoils depositing 60 keV of energy. The detector performance reported here meets the requirements needed to achieve the principal scientific goals of the ReD experiment in the search for a directional effect due to columnar recombination. A phenomenological parameterisation of the recombination probability in LAr is presented and employed for modeling the dependence of scintillation quenching and charge yield on the drift field for electron recoils between 50–500 keV and fields up to 1000 V/cm. 

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4. Constraints on directionality effect of nuclear recoils in a liquid argon time projection chamber

   https://doi.org/10.1140/epjc/s10052-023-12312-1  

   DarkSide-20k Collaboration ; Agnes, P. ; Ahmad, I. ; Albergo, S. ; Albuquerque, I. F. M. ; Alexander, T. ; Alton, A. K. ; Amaudruz, P. ; Corona, M. Atzori ; Ave, M. ; et al ( January 2024 , The European Physical Journal C)

   The direct search for dark matter in the form of weakly interacting massive particles (WIMP) is performed by detecting nuclear recoils produced in a target material from the WIMP elastic scattering. The experimental identification of the direction of the WIMP-induced nuclear recoils is a crucial asset in this field, as it enables unmistakable modulation signatures for dark matter. The Recoil Directionality (ReD) experiment was designed to probe for such directional sensitivity in argon dual-phase time projection chambers (TPC), that are widely considered for current and future direct dark matter searches. The TPC of ReD was irradiated with neutrons at the INFN Laboratori Nazionali del Sud. Data were taken with nuclear recoils of known directions and kinetic energy of 72 keV, which is within the range of interest for WIMP-induced signals in argon. The direction-dependent liquid argon charge recombination model by Cataudella et al. was adopted and a likelihood statistical analysis was performed, which gave no indications of significant dependence of the detector response to the recoil direction. The aspect ratioRof the initial ionization cloud is$$R < 1.072$$$R<1.072$with 90 % confidence level.

    

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5. Production and validation of scintillating structural components from low-background Poly(ethylene naphthalate)

   https://doi.org/10.1088/1748-0221/17/01/P01010  

   Efremenko, Y. ; Febbraro, M. ; Fischer, F. ; Guitart Corominas, M. ; Gusev, K. ; Hackett, B. ; Hayward, C. ; Hodák, R. ; Krause, P. ; Majorovits, B. ; et al ( January 2022 , Journal of Instrumentation)

   Abstract Poly Ethylene Naphthalate (PEN) is an industrial polymer plastic which is investigated as a low background, transparent, scintillating and wavelength shifting structural material. PEN scintillates in the blue region and has excellent mechanical properties both at room and cryogenic temperatures. Thus, it is an ideal candidate for active structural components in experiments for the search of rare events like neutrinoless double-beta decay or dark matter recoils. Such optically active structures improve the identification and rejection efficiency of backgrounds events, like this improving the sensitivity of experiments. This paper reports on the production of radiopure and transparent PEN plates These structures can be used to mount germanium detectors operating in cryogenic liquids (LAr, LN). Thus, as first application PEN holders will be used to mount the Ge detectors in the Legend -200 experiment. The whole process from cleaning the raw material to testing the PEN active components under final operational conditions is reported. 

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