We report here the results of a nonrelativistic effective field theory (EFT) WIMP search analysis using LUX data. We build upon previous LUX analyses by extending the search window to include nuclear ...recoil energies up to ∼ 180 keVnr, requiring a reassessment of data quality criteria and background models. In order to use an unbinned profile likelihood statistical framework, the development of new analysis techniques to account for higher-energy backgrounds was required. With a 3.14 × 104 kg ⋅ day exposure using data collected between 2014 and 2016, we find our data is compatible with the background expectation and set 90% C.L. exclusion limits on nonrelativistic EFT WIMP-nucleon couplings, improving upon previous LUX results and providing constraints on a EFT WIMP interactions using the { neutron , proton } interaction basis. Additionally, we report exclusion limits on inelastic EFT WIMP-isoscalar recoils that are competitive and world-leading for several interaction operators.
Superfluid $^4$He is a promising target material for direct detection of light ($<$ 1 GeV) dark matter. Possible signal channels available for readout in this medium include prompt photons, triplet ...excimers, and roton and phonon quasiparticles. The relative yield of these signals has implications for the sensitivity and discrimination power of a superfluid $^4$He dark matter detector. Using a 16~cm$^3$ volume of 1.75~K superfluid $^4$He read out by six immersed photomultiplier tubes, we measured the scintillation from electronic recoils ranging between 36.3 and 185~keV$_\mathrm{ee}$, yielding a mean signal size of $1.25^{+0.03}_{-0.03}$~phe/keV$_\mathrm{ee}$, and nuclear recoils from 53.2 to 1090~keV$_\mathrm{nr}$. We compare the results of our relative scintillation yield measurements to an existing semiempirical model based on helium-helium and electron-helium interaction cross sections. As a result, we also study the behavior of delayed scintillation components as a function of recoil type and energy, a further avenue for signal discrimination in superfluid $^4$He.
A backing detector for order-keV neutrons Biekert, A.; Chaplinsky, L.; Fink, C.W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2022, Letnik:
1039
Journal Article
Recenzirano
Odprti dostop
We have designed and tested a large-area (0.15 m2) neutron detector based on neutron capture on 6Li. The neutron detector design has been optimized for the purpose of tagging the scattering angle of ...keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (<100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CEνNS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of ∼25% at the relevant O(keV) neutron energies, and with a mean capture time of ∼17μs. The prototype was characterized using a 252Cf neutron source and agreement with the simulation was observed within a few percent level.
A backing detector for order-keV neutrons Biekert, A.; Chaplinsky, L.; Fink, C. W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2022, Letnik:
1039
Journal Article
Recenzirano
Odprti dostop
In this work, we have designed and tested a large-area (0.15 m2) neutron detector based on neutron capture on 6Li. The neutron detector design has been optimized for the purpose of tagging the ...scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy (<100 eV) nuclear recoil in detectors for dark matter and coherent elastic neutrino nucleus scattering (CE$\textit{v}$NS). We describe the design, construction, and characterization of a prototype. The prototype is designed to have a tagging efficiency of ~25% at the relevant $\mathcal{O}$(keV) neutron energies, and with a mean capture time of ~ 17 μs. The prototype was characterized using a 252Cf neutron source and agreement with the simulation was observed within a few percent level.
We present the results of a direct detection search for mirror dark matter interactions, using data collected from the Large Underground Xenon experiment during 2013, with an exposure of 95 ...live−days×118 kg. Here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the Earth. Annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. Having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.9 keV. This limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. We exclude mirror electron temperatures above 0.3 keV at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature.
The title compound methyl(2E)-2-{N-(2-formylphenyl) (4-methylbenzene)sulfonamidomethyl}-3-(4-chlorophenyl) prop-2-enoate (MFMSC) has been synthesized and single crystals were grown by slow ...evaporation solution growth technique at room temperature. Structural and vibrational spectroscopic studies were carried out by using single crystal X-ray diffraction, FT-IR and NMR spectral analysis together with DFT method using Gaussian'03 software. The detailed interpretation of the vibrational spectra has been carried out by VEDA program. NBO analysis, Mulliken charge analysis, HOMO-LUMO, MEP, Global chemical reactivity descriptors and thermodynamic properties have been analyzed. The hyperpolarisability calculation reveals the present material has a reasonably good propensity for nonlinear optical activity. The obtained antimicrobial activity results indicate that the compound shows good to moderate activity against all tested bacterial and fungal pathogens. A computational study was also carried out to predict the drug-likeness and ADMET properties of the title compound. Due to the different potential biological activity of the title compound, molecular docking study is also reported and the compound might exhibit inhibitory activity against penicillin-binding protein PBP-2X.
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•Structural and spectral investigation of MFMSC was carried out.•NBO analysis, HOMO and LUMO energies and MEP distribution of the molecule were theoretically predicted.•Thermo dynamical properties at different temperatures were calculated.•In vitro antimicrobial activity and Molecular docking studies were reported.
A siliconized epoxy interpenetrating network (IPN) was synthesized from commercially available DGEBA epoxy resin GY250 (Ciba-Geigy, epoxy equivalent = 182–192, viscosity = 9000–12000 cP) and hydroxyl ...terminated polydimethylsiloxane (PDMS). PDMS and GY250 were thoroughly mixed at 30°C to get the prepolymer. Stoichiometric amounts of PDMS-epoxy prepolymer, γ-aminopropyltriethoxysilane, aliphatic amine curing agent (HY951), and dibutyltindilaurate catalyst, were thoroughly mixed and cast in a mould after evacuating the entrapped air. The cured material was then taken out and post cured at 70°C for 10 h. IPN was characterized by FTIR spectroscopy, SEM, DSC, TGA and viscosity measurements. Incorporation of PDMS in the epoxy matrix increased the viscosity and lowered the exotherm and pot-life. PDMS in IPN increasedTg, heat-distortion temperature and reduced the percentage weight loss with increase in temperature. Incorporation of PDMS drastically reduced the tensile and flexural strengths and hardness. By reducing the tensile and flexural modulus, the siloxane moiety effectively reduced the internal stress of IPN thereby improving its impact strength and percentage elongation. PDMS increased the electric potential gradient of IPN to withstand without breakdown. An increase in the tracking index and arc resistance of IPN were observed, because of the presence of Si-O-Si, which minimized the possibility of forming carbonized path. Volume and surface resistivities of IPN also increased with the incorporation of PDMS. The siliconized epoxy IPN, with better impact and thermal resistance, may be used in automobile and aerospace applications to withstand high temperature, and mechanical stress. The PDMS-epoxy IPN may be used for encapsulation, high temperature and high voltage application due to their low shrinkage and lesser internal stress. With the improved electrical characteristics, IPN may be used for high performance electrical insulation, insulator housings, and encapsulation to withstand high voltage, moisture, oxidation, chemical attack, biological attack, outdoor weathering, contamination, electrical, mechanical and thermal stress.
Abstract
A portable monoenergetic 24 keV neutron source based on the
124
Sb-
9
Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron ...energy from SbBe and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from
124
Sb decays while letting through the neutrons. To increase the
124
Sb activity and thus the neutron flux, a >1 GBq
124
Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20–25 keV to be 6.00±0.30 neutrons per cm
2
per second and the total gamma flux to be 245±8 gammas per cm
2
per second (numbers scaled to 1 GBq activity of the
124
Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.
This work details the development of a three-dimensional (3D) electric field model for the LUX detector. The detector took data to search for weakly interacting massive particles (WIMPs) during two ...periods. After the first period completed, a time-varying non-uniform negative charge developed in the polytetrafluoroethylene (PTFE) panels that define the radial boundary of the detector's active volume. This caused electric field variations in the detector in time, depth and azimuth, generating an electrostatic radially-inward force on electrons on their way upward to the liquid surface. To map this behavior, 3D electric field maps of the detector's active volume were generated on a monthly basis. This was done by fitting a model built in COMSOL Multiphysics to the uniformly distributed calibration data that were collected on a regular basis. The modeled average PTFE charge density increased over the course of the exposure from -3.6 to −5.5μC/m2. From our studies, we deduce that the electric field magnitude varied locally while the mean value of the field of ∼200 V/cm remained constant throughout the exposure. As a result of this work the varying electric fields and their impact on event reconstruction and discrimination were successfully modeled.
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