Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H10: Dark Matter: Galactic and ExtragalacticLive
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Sponsoring Units: DAP Chair: Risa Wechsler, Stanford |
Sunday, April 18, 2021 10:45AM - 10:57AM Live |
H10.00001: Dark Matter Search Results from DAMIC at SNOLAB Alexander Piers The DAMIC experiment at SNOLAB uses thick, fully-depleted, scientific grade charge-coupled devices (CCDs) to search for the interactions between proposed dark matter particles in the galactic halo and the ordinary silicon atoms in the detector. DAMIC CCDs operate with an extremely low instrument noise and dark current, making them particularly sensitive to ionization signals expected from low-mass dark matter particles. For the past two years, DAMIC has collected dark-matter search data with an array of seven CCDs (40-gram target) installed in a low radiation environment in the SNOLAB underground laboratory. This talk will focus on the recent dark matter search results from DAMIC. We will present the search methodology and results from an 11 kg day exposure WIMP search, including the strictest limit on the WIMP-nucleon cross section for a silicon target for $m_\chi < 9 \ \rm GeV \ c^{-2}$. Additionally, we will discuss recent limits on light dark matter that could interact with the electrons of the silicon atoms. [Preview Abstract] |
Sunday, April 18, 2021 10:57AM - 11:09AM Live |
H10.00002: Experimental signatures of a new dark matter WIMP Roland Allen, Reagan Thornberry, Maxwell Throm, John Killough, Dylan Blend, Michael Erickson, Brian Sun, Brett Bays, Gabriel Frohaug The dark matter WIMP proposed here has the following properties: (1)~Its mass is $\le 125$ GeV. (2)~It will yield the observed dark matter abundance if its mass is $\sim$~75~GeV. (3)~The cross-section for nuclear scattering is consistent with the limits from direct detection experiments, (4)~the cross-section for collider production is consistent with limits from the LHC, and (5)~the cross-section for annihilation is consistent with the general (multiple-channel) limits from gamma-ray observations of dwarf spheroidal galaxies. The mass and annihilation cross-section (through 29 different channels) are in agreement with (6)~analyses of the observations of gamma rays from the Galactic center by Fermi-LAT and (7)~analyses of the antiprotons observed by AMS-02 (with both supporting the hypothesis of WIMP annihilation). (8)~The most promising signature for collider detection appears to be missing transverse energy of $\gtrsim$ 150 GeV following creation through vector boson fusion. (9)~The best hope for direct detection is still Higgs exchange. (10)~The present dark matter particle and the lightest neutralino of supersymmetry (susy) can stably coexist in a multicomponent dark matter scenario. This new dark matter candidate results from an extended Higgs sector with or without susy. [Preview Abstract] |
Sunday, April 18, 2021 11:09AM - 11:21AM Live |
H10.00003: Fundamental Particle Physics with SWGO Andrea Albert The Southern Wide-field Gamma-ray Observatory (SWGO) is a proposed experiment that will continuously monitor the TeV gamma-ray sky. Similar to the High Altitude Water Cherenkov (HAWC) Observatory, it will have a wide field of view, nearly 100% duty cycle, and will therefore observe ~2/3 of the sky every day. It will use water Cherenkov detectors and be located in the Southern Hemisphere. SWGO is planned to be the most sensitive gamma-ray observatory in the Southern Hemisphere above ~10 TeV. SWGO will be able to perform several searches for physics beyond the Standard Model. Being located in the Southern Hemisphere will allow for searches for dark matter signals in key targets like the Galactic Center and newly discovered dwarf galaxies like Reticulum II. SWGO will also be able to search for primordial black holes, axion like particles, and Lorentz invariance violation. [Preview Abstract] |
Sunday, April 18, 2021 11:21AM - 11:33AM Live |
H10.00004: Combined Dark Matter Searches Towards Dwarf Spheroidal Galaxies with Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS Daniel Salazar-Gallegos Solving the Dark Matter (DM) problem will likely reveal physics beyond the Standard Model. The search for DM is challenging, so searches are using a variety of techniques. For indirect DM searches, Dwarf spheroidal galaxies (dSphs) are prime targets because their ratio of DM content to baryonic is high. We propose a novel observation technique through multiple gamma-ray observatories. We established a collaboration of three Imaging Air Cherenkov Telescope (IACT) arrays: H.E.S.S., MAGIC, and VERITAS; the Fermi-LAT satellite, and the water Cherenkov detector, HAWC. Our collaboration is meant to maximize the sensitivity of DM searches towards dSphs by combining dSph data for the first time. Techniques are diverse across these experiments, so each group analyze their individual datasets from multiple dSph's in their fields of view then combine these data at the likelihood level. We use a common set of annihilation channels in analysis and a common treatment of the astrophysical factor for consistency across experiments. We use a common statistical treatment of instrumental systematic uncertainties. We present our results as limits to the velocity weighted cross section for DM-DM annihilation as a function of DM mass. Our limits will be the strictest for indirect detection to date. [Preview Abstract] |
Sunday, April 18, 2021 11:33AM - 11:45AM Live |
H10.00005: Prompt and Delayed Cosmic-Ray Muon Induced Neutron Backgrounds in Direct Detection Dark Matter Searches Sagar Sharma Poudel Direct detection experiments try to detect low energy scattering of dark matter off the atomic nuclei target. Neutrons are an important background to the WIMPs (Weakly Interacting Massive Particles) dark matter searches in underground detectors. I will talk about two class of neutron backgrounds that arise from the cosmic-ray muon and the resulting interactions, 1) Prompt cosmogenic neutron backgrounds which have the neutron interaction in coincidence with the original muon or muon-induced shower, and 2) Delayed neutron backgrounds from the cosmogenic activation in materials and/or induced radioactivity. In this presentation, I will talk about my FLUKA-simulations based study of the backgrounds of cosmic-ray muon induced (cosmogenic) neutrons for WIMP searches with the DarkSide-20k, the liquid-argon based direct detection dark matter experiment to be commissioned by GADMC (The Global Argon Dark Matter Collaboration). The FLUKA-simulations based study was carried out to estimate the efficiency of DarkSide-20k's detector system to veto/shield cosmogenic neutrons, and to estimate the cosmogenic neutron background rate for WIMP dark matter searches. [Preview Abstract] |
Sunday, April 18, 2021 11:45AM - 11:57AM Live |
H10.00006: Background Studies for the LUX-ZEPLIN Dark Matter Experiment Dongqing Huang The LZ detector is a dual-phase time projection chamber (TPC) aiming to detect rare events resulting from the scattering of Weakly Interacting Massive Particles (WIMPs), a leading dark matter candidate. Significant effort has been made to achieve an unprecedented low background rate within its fiducial volume, including extensive detector material screenings and an inline radon removal system, to reach a target sensitivity of 1.4 x 10$^{-48}$ cm$^2$ at 40 GeV / c$^2$. In preparation for upcoming LZ science runs, we present here using simulated data rigorous studies of both the expected residual backgrounds as well as possible anomalous events. A thorough understanding of these backgrounds is critical for eventual definite identifications of dark matter events in the LZ experiment. [Preview Abstract] |
Sunday, April 18, 2021 11:57AM - 12:09PM Live |
H10.00007: An estimation of the mass of fermionic dark matter Ahmad Borzou After nearly a century of hypothesizing the existence of dark matter, its mass is still unknown. In this work, we attempt to estimate the mass of fermionic dark matter. We place a lower bound on the dispersion velocity of dark matter using its positiveness. We show that the lowest dispersion velocity corresponds with the Virial state. We draw two conclusions by analyzing the observationally constructed best-fit mass models of a set of late-type galaxies. First, we show that the logarithm of the halo masses is directly proportional to the logarithm of their dispersion velocities, indicating that the halos are virialized. Second, we show that the dark matter mass over its temperature at the edge of the halos is nearly the same in all of the analyzed galaxies. The latter universality suggests that the temperature of dark matter at the edge of halos is set by its primordial history and is independent of halos' environment. Therefore, we estimate the mass of dark matter in terms of its freeze-out temperature in the early universe. [Preview Abstract] |
Sunday, April 18, 2021 12:09PM - 12:21PM Live |
H10.00008: Axial Symmetry Tests of Milky Way Disk Stars Probe the Galaxy's Matter Distribution Austin Hinkel, Susan Gardner, Brian Yanny In this talk, we show how tests of axial symmetry of the Galaxy can be realized with Gaia DR2, and consider what these tests reveal about the Galaxy's matter distribution. Namely, we apply a form of Noether's Theorem, vis-a-vis tests of axial symmetry, to probe the quality of the angular momentum about the axis normal to the Galactic plane as an integral of motion. We show how this failure of this symmetry speaks to a Milky Way that is not isolated and not in steady-state. Additionally, we show that a prolate form of the gravitational distortion of the Galaxy by the Magellanic Clouds, determined from Orphan stream fits by Erkal et al., 2019, is compatible with the axial symmetry-breaking we have discovered, and that a localized, abrupt change in the asymmetry closer to the Galactic center reveals a resonance of the Galactic bar. Finally, we outline recent findings concerning the small-scale structure of our Galaxy, with potential ramifications for dark matter candidates. [Preview Abstract] |
Sunday, April 18, 2021 12:21PM - 12:33PM Live |
H10.00009: Comparing cold dark matter, interacting dark matter and modified Newtonian dynamics using galaxy rotation curves: data favors a dark matter disk Nicolas Loizeau, Glennys Farrar We compare 8 different dark matter models on an equal footing using 159 high quality rotation curves with gas and stars distributions (SPARC database). We pay special attention to the handling of the stellar mass-to-light ratios. The compared models are: two non-interacting dark matter models (NFW and pseudo-isothermal), a self interacting DM model, two hadronically interacting DM models, a total-baryon-rescaling model and two modified Newtonian dynamics type models: the historical MOND, and the recently developed Radial Acceleration Relation (McGaugh et al). The models with Gas-DM interactions generate a disky component in the dark matter, which significantly improves the fits to the rotation curves compared to all other models. The effective Gas-DM interaction needed to produce the required DM disk component is compatible with currents limits on DM-baryon interactions from the CMB and direct detection experiments. It remains to be determined whether gravitational effects alone can also produce sufficient deviation from an spherically-symmetric CDM halo to agree with the rotation curve data. [Preview Abstract] |
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