Axion-like particles (ALPs) are pseudo-scalar particles that are candidates for ultralight dark matter. ALPs interact with photons slightly and cause the rotational oscillation of linear polarization. DANCE searches for ALP dark matter by enhancing the rotational oscillation in a bow-tie ring cavity. The signal to noise ratio of DANCE can be improved by long-term observation, and we are planning a year-long observation for the final DANCE. In this document, I will report on the control systems of the ring cavity we developed for the future long-term observation.
The DAMIC experiment uses fully depleted, high resistivity CCDs to search for dark matter particles. With an energy threshold $sim$50 eV$_{ee}$, and excellent energy and spatial resolutions, the DAMIC CCDs are well-suited to identify and suppress radioactive backgrounds, having an unrivaled sensitivity to WIMPs with masses $<$6 GeV/$c^2$. Early results motivated the construction of a 100 g detector, DAMIC100, currently being installed at SNOLAB. This contribution discusses the installation progress, new calibration efforts near the threshold, a preliminary result with 2014 data, and the prospects for physics results after one year of data taking.
The sensitivity of experimental searches for axion dark matter coupled to photons is typically proportional to the strength of the applied static magnetic field. We demonstrate how a permeable material can be used to enhance the magnitude of this static magnetic field, and therefore improve the sensitivity of such searches in the low frequency lumped-circuit limit. Using gadolinium iron garnet toroids at temperature 4.2 K results in a factor of 4 enhancement compared to an air-core toroidal design. The enhancement is limited by magnetic saturation. Correlation of signals from three such toroids allows efficient rejection of systematics due to electromagnetic interference. The sensitivity of a centimeter-scale axion dark matter search based on this approach is on the order of $g_{agammagamma}approx10^{-9}$ GeV$^{-1}$ after 8 hours of data collection for axion masses near $10^{-10}$ eV. This approach may substantially extend the sensitivity reach of large-volume lumped element axion dark matter searches.
The highly radiopure NaI(Tl) was developed to search for particle candidates of dark matter. The optimized methods were combined to reduce various radioactive impurities. The $^{40}$K was effectively reduced by the re-crystallization method. The progenies of the decay chains of uranium and thorium were reduced by appropriate resins. The concentration of natural potassium in NaI(Tl) crystal was reduced down to 20 ppb. Concentrations of alpha-ray emitters were successfully reduced by appropriate selection of resin. The present concentration of thorium series and 226Ra were $1.2 pm1.4$ $mu$Bq/kg and $13pm4$ $mu$Bq/kg, respectively. No significant excess in the concentration of $^{210}$Pb was obtained, and the upper limit was 5.7 $mu$Bq/kg at 90% C. L. The achieved level of radiopurity of NaI(Tl) crystals makes construction of a dark matter detector possible.
This Letter reports results from a haloscope search for dark matter axions with masses between 2.66 and 2.81 $mu$eV. The search excludes the range of axion-photon couplings predicted by plausible models of the invisible axion. This unprecedented sensitivity is achieved by operating a large-volume haloscope at sub-kelvin temperatures, thereby reducing thermal noise as well as the excess noise from the ultra-low-noise SQUID amplifier used for the signal power readout. Ongoing searches will provide nearly definitive tests of the invisible axion model over a wide range of axion masses.
MeV-GeV dark matter (DM) is theoretically well motivated but remarkably unexplored. This Letter of Intent presents the MeV-GeV DM discovery potential for a 1 m$^3$ segmented plastic scintillator detector placed downstream of the beam-dump at one of the high intensity JLab experimental Halls, receiving up to 10$^{22}$ electrons-on-target (EOT) in a one-year period. This experiment (Beam-Dump eXperiment or BDX) is sensitive to DM-nucleon elastic scattering at the level of a thousand counts per year, with very low threshold recoil energies ($sim$1 MeV), and limited only by reducible cosmogenic backgrounds. Sensitivity to DM-electron elastic scattering and/or inelastic DM would be below 10 counts per year after requiring all electromagnetic showers in the detector to exceed a few-hundred MeV, which dramatically reduces or altogether eliminates all backgrounds. Detailed Monte Carlo simulations are in progress to finalize the detector design and experimental set up. An existing 0.036 m$^3$ prototype based on the same technology will be used to validate simulations with background rate estimates, driving the necessary R$&$D towards an optimized detector. The final detector design and experimental set up will be presented in a full proposal to be submitted to the next JLab PAC. A fully realized experiment would be sensitive to large regions of DM parameter space, exceeding the discovery potential of existing and planned experiments by two orders of magnitude in the MeV-GeV DM mass range.
Hiroki Fujimoto
,Yuka Oshima
,Masaki Ando
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(2021)
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"Dark matter Axion search with riNg Cavity Experiment DANCE: Development of control system for long-term measurement"
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Hiroki Fujimoto
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