We present a novel approach for the search of dark matter in the DarkSide-50 experiment, relying on Bayesian Networks. This method incorporates the detector response model into the likelihood ...function, explicitly maintaining the connection with the quantity of interest. No assumptions about the linearity of the problem or the shape of the probability distribution functions are required, and there is no need to morph signal and background spectra as a function of nuisance parameters. By expressing the problem in terms of Bayesian Networks, we have developed an inference algorithm based on a Markov Chain Monte Carlo to calculate the posterior probability. A clever description of the detector response model in terms of parametric matrices allows us to study the impact of systematic variations of any parameter on the final results. Our approach not only provides the desired information on the parameter of interest, but also potential constraints on the response model. Our results are consistent with recent published analyses and further refine the parameters of the detector response model.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The EDELWEISS Collaboration is searching for WIMP dark matter using natural Ge cryogenic detectors. The whole data set of the first phase of the experiment contains a fiducial exposure of 4.8 kg day ...on 73Ge, the naturally present (7.8%), high-spin Ge isotope. The sensitivity of the experiment to the spin-dependent WIMP-nucleon interactions is evaluated using the model-independent framework proposed by Tovey et al. Phys. Lett. B 488 (2000) 17. It is shown that the EDELWEISS sensitivity for the WIMP-neutron coupling is competitive when compared with results of other spin-sensitive WIMP dark matter experiments. The current experimental limits lie however two orders of magnitude higher than the most optimistic SUSY models.
A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid ...argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ∼107, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ∼3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.
Finding unequivocal evidence of dark matter interactions in a particle detector is a major goal of research in physics. Liquid argon time projection chambers offer a path to probe Weakly Interacting ...Massive Particles scattering cross sections on nuclei down to the so-called neutrino floor, in a mass range from a few GeV to hundreds of TeV. Based on the successful operation of the DarkSide-50 detector at LNGS, a new and more sensitive experiment, DarkSide-20k, has been designed and is now under construction. A thorough understanding of the DarkSide-50 detector response and, therefore, of all types of events observed in the detector, is essential for the optimal design of the new experiment. In this article, we report on a specific set of events, namely, standard two-pulse scintillation–ionization signals with a third small amplitude pulse, occurring within the 440μs data acquisition window of standard events. Some of these events are due to the photoionization of the TPC cathode. We compare our results with those published by collaborations using liquid xenon time projection chambers, which observed a similar phenomenon, and, in particular, with a recent paper by the LUX Collaboration (D.S. Akerib et al. Phys.Rev.D 102, 092004 (2020)) From the measured rate of these events, we estimate for the first time the quantum efficiency of the tetraphenyl butadiene deposited on the DarkSide-50 cathode at wavelengths of around 128 nm, in liquid argon. Also, both experiments observe events likely related to the photoionization of impurities in the liquid. The probability of photoelectron emission per unit length turns out to be an order of magnitude lower in DarkSide-50 than in LUX.
Following a dedicated R&D program, ASG Superconductors has recently developed techniques for designing and constructing open cryogen free MRI magnets, refrigerated by two double stage cryocoolers ...only. The magnet consists of two coils both made with six double pancakes, each double pancake being obtained reacting and winding 1600 m of multifilamentary, copper-stabilized MgB2 tape supplied by Columbus Superconductors. Here we report the thermal and electromagnetic characterization and the achieved targets of the first prototype, evaluated on a long term activity period. The MRI images, acquired starting from November 2006, further demonstrate the accomplishment of remarkable magnet performances. In parallel to the long term tests on the first prototype, ASG Superconductors has designed and constructed a second MRI magnet with improved characteristics. We present here the related test results and a comparison with the previous ones.
Precision measurements of solar neutrinos emitted by specific nuclear reaction chains in the Sun are of great interest for developing an improved understanding of star formation and evolution. Given ...the expected neutrino fluxes and known detection reactions, such measurements require detectors capable of collecting neutrino-electron scattering data in exposures on the order of 1 ktonne-yr, with good energy resolution and extremely low background. Two-phase liquid argon time projection chambers (LAr TPCs) are under development for direct Dark Matter WIMP searches, which possess very large sensitive mass, high scintillation light yield, good energy resolution, and good spatial resolution in all three cartesian directions. While enabling Dark Matter searches with sensitivity extending to the ''neutrino floor'' (given by the rate of nuclear recoil events from solar neutrino coherent scattering), such detectors could also enable precision measurements of solar neutrino fluxes using the neutrino-electron elastic scattering events. Modeling results are presented for the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). The results show that such a detector could measure the CNO neutrino rate with ∼15% precision, and significantly improve the precision of the {sup 7}Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector.
Abstract Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., ...Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of $${^{39}\hbox {Ar}}$$ 39 Ar in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, $${^{39}\hbox {Ar}}$$ 39 Ar is a $$\beta $$ β -emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Following a dedicated R&D program, ASG Superconductors has recently developed techniques for designing and constructing open cryogen free MRI magnets, refrigerated by two double stage cryocoolers ...only. The magnet consists of two coils both abstract truncated by publisher.
We reanalize data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei ...with an effective field theory framework. The dataset corresponds to a total (16660 $\pm$ 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between $2.4 \times 10^{-45} \, \mathrm{cm}^2$ and $2.3 \times 10^{-42} \, \mathrm{cm}^2$ (8.9 $\times 10^{-45} \, \mathrm{cm}^2$ and 6.0 $\times 10^{-42} \, \mathrm{cm}^2$) for WIMPs of mass of 100 $\mathrm{GeV/c^2}$ (1000 $\mathrm{GeV/c^2}$) at 90\% confidence level.
A superconducting transition edge sensor microcalorimeter was tested at the synchrotron radiation beam-line of the ESRF to collect the X-ray fluorescence spectrum of a Renaissance gold lustre on ...ceramic. The measured energy resolution of the detector in the range 6–9keV was 70eV, i.e. 3 times better than that of the usual solid state detector. The preliminary data collected demonstrate the applicability of these detectors to the energy dispersive X-ray spectroscopy at the synchrotron radiation facilities.
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