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Dark Matter Search Results from the CDMS II Experiment
The CDMS II Collaboration
Astrophysical observations indicate that dark matter constitutes most of the mass in our universe, but its nature remains unknown. Over the past decade, the Cryogenic Dark Matter Search (CDMS II) experiment has provided world-leading sensitivity for the direct detection of weakly interacting massive particle (WIMP) dark matter. The final exposure of our low-temperature germanium particle detectors at the Soudan Underground Laboratory yielded two candidate events, with an expected background of 0.9 ± 0.2 events. This is not statistically significant evidence for a WIMP signal. The combined CDMS II data place the strongest constraints on the WIMP-nucleon spin-independent scattering cross section for a wide range of WIMP masses and exclude new parameter space in inelastic dark matter models.
Design Overview of the DM Radio Pathfinder Experiment
Maximiliano Silva-Feaver, Saptarshi Chaudhuri, Hsiao-Mei Cho, Carl Dawson, Peter Graham, Kent Irwin, Stephen Kuenstner, Dale Li, Jeremy Mardon, Harvey Moseley, Richard Mule, Arran Phipps, Surjeet Rajendran, Zach Steffen, Betty Young
We introduce the DM Radio, a dual search for axion and hidden photon dark matter using a tunable superconducting lumped-element resonator. We discuss the prototype DM Radio Pathfinder experiment, which will probe hidden photons in the 500 peV (100 kHz)-50 neV (10 MHz) mass range. We detail the design of the various components: the LC resonant detector, the resonant frequency tuning procedure, the differential SQUID readout circuit, the shielding, and the cryogenic mounting structure. We present the current status of the pathfinder experiment and illustrate its potential science reach in the context of the larger experimental program.
Links : https://arxiv.org/abs/1610.09344
Dark matter decay through gravity portals
Oscar Catà, Alejandro Ibarra, Sebastian Ingenhütt
Motivated by the fact that, so far, the whole body of evidence for dark matter is of gravitational origin, we study the decays of dark matter into Standard Model particles mediated by gravity portals, i.e., through nonminimal gravitational interactions of dark matter. We investigate the decays in several widely studied frameworks of scalar and fermionic dark matter where the dark matter is stabilized in flat spacetime via global symmetries. We find that the constraints on the scalar singlet dark matter candidate are remarkably strong and exclude large regions of the parameter space, suggesting that an additional stabilizing symmetry should be in place. In contrast, the scalar doublet and the fermionic singlet candidates are naturally protected against too fast decays by gauge and Lorentz symmetry, respectively. For a nonminimal coupling parameter ξ∼O(1), decays through the gravity portal are consistent with observations if the dark matter mass is smaller than ∼105 GeV, for the scalar doublet, and ∼106 GeV, for the fermionic singlet.
Links : https://arxiv.org/abs/1611.00725
Patrick deNiverville, Chien-Yi Chen, Maxim Pospelov, Adam Ritz
We analyze the prospects for detection of light sub-GeV dark matter produced in experiments designed to study the properties of neutrinos, such as MiniBooNE, T2K, SHiP, DUNE etc. We present an improved production model, when dark matter couples to hadronic states via a dark photon or baryonic vector mediator, incorporating bremsstrahlung of the dark vector. In addition to elastic scattering, we also study signatures of light dark matter undergoing deep inelastic or quasi-elastic NCπ0-like scattering in the detector producing neutral pions, which for certain experiments may provide the best sensitivity.
An extensive appendix provides documentation for a publicly available simulation tool {\tt BdNMC} that can be applied to determine the hidden sector dark matter production and scattering rate at a range of proton fixed target experiments
Links : https://arxiv.org/abs/1609.01770
The effect of dark matter velocity profile on directional detection of dark matter
Ranjan Laha
Directional detection is an important way to detect dark matter. An input to these experiments is the dark matter velocity distribution. Recent hydrodynamical simulations have shown that the dark matter velocity distribution differs substantially from the Standard Halo Model. We study the impact of some of these updated velocity distribution in dark matter directional detection experiments. We calculate the ratio of events required to confirm the forward-backward asymmetry and the existence of the ring of maximum recoil rate using different dark matter velocity distributions for 19F and Xe targets. We show that with the use of updated dark matter velocity profiles, the forward-backward asymmetry and the ring of maximum recoil rate can be confirmed using a factor of ∼2 -- 3 less events when compared to that using the Standard Halo Model.
Links : https://arxiv.org/abs/1610.08632
Gamma Rays From Dark Matter Subhalos Revisited: Refining the Predictions and Constraints
Dan Hooper, Samuel J. Witte
Utilizing data from the ELVIS and Via Lactea-II simulations, we characterize the local dark matter subhalo population, and use this information to refine the predictions for the gamma-ray fluxes arising from annihilating dark matter in this class of objects. We find that the shapes of nearby subhalos are significantly altered by tidal effects, and are generally not well described by NFW density profiles, instead prefering power-law profiles with an exponential cutoff. From the subhalo candidates detected by the Fermi Gamma-Ray Space Telescope, we place limits on the dark matter annihilation cross section that are only modestly weaker than those based on observations of dwarf galaxies. We also calculate the fraction of observable subhalos that are predicted to be spatially extended at a level potentially discernible to Fermi.
Links : https://arxiv.org/abs/1610.07587
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