Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session X07: Axion II / Dark MatterRecordings Available
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Sponsoring Units: DPF Chair: Hugh Lippincott, University of California, Santa Barbara Room: Salon 4 |
Tuesday, April 12, 2022 10:45AM - 10:57AM |
X07.00001: ADMX Run 2A: A Multi-Cavity QCD Axion Search Stefan P Knirck The QCD axion is among the best motivated particle dark matter (DM) candidates. Cavity haloscopes like ADMX (Axion Dark Matter eXperiment) resonantly detect conversion of DM axions to photons under a strong magnetic field in a high-Q resonant cavity. Recent ADMX runs with a single cavity excluded most of the QCD axion parameter range between 2.7μeV and 4.2μeV and are set to cover the range until about 5.4μeV. However, at higher masses the wavelength of the generated photons shrinks, generally leading to a smaller cavity volume and reduced sensitivity. In this talk we present an array of four cavities, tuning in sync to scan a broad mass range from 5.4μeV to 7.6μeV with QCD axion sensitivity. We discuss experimental measurements of the quality factor and other important electromagnetic characteristics at room temperature and 4K. We show recent R&D and experimental improvements, and outline the path towards commissioning and run of the full axion search experiment. |
Tuesday, April 12, 2022 10:57AM - 11:09AM |
X07.00002: ADMX-Extended Frequency Range: 2-4 GHz Search Alexander T Hipp The Axion Dark Matter eXperiment (ADMX) is a microwave cavity search for axions in the galactic halo. At present, ADMX has scanned the 600 MHz to 1 GHz frequency range. There are plans to extend the search and scan higher frequency regions. One design in particular consists of an array of cavities that will be tuned over the 2-4 GHz frequency range. The current baseline design is to use 18 identical cavities in a 9.4 T 800 mm diameter magnet. In this talk, we will discuss the concept, design, and preliminary results from experiments on prototype cavities to be used in this search. |
Tuesday, April 12, 2022 11:09AM - 11:21AM |
X07.00003: Dielectric-Loaded Cavities for ADMX Low-Frequency Searches Mohamed A Hassan, Joseph R Gleason, Andrew Sonnenschein Axion dark matter searches using the resonant cavity technique are limited at low mass by the physical cavity size. Previous experiments by the ADMX collaboration have reached masses as low as 1.9 μeV using a 50 cm diameter cylindrical cavity. Because of the fixed size magnet limitation, a large empty cavity is not generally a possibility at lower frequencies. Reentrant cavities can operate at a lower frequency for a given diameter and allow access to a lower axion mass range. However, this comes with a penalty on the form factor. Moreover, tuning a reentrant cavity would likely involve moving a tuning rod in and out of the cavity, which could complicate the design of the tuning system. This talk will show an elegant alternative technique based on loading the cavity with dielectric rods, which brings the frequency down depending on the dielectric loading. Furthermore, the dielectric rods can be arranged to allow a rotational movement of a metallic tuning rod, which is a well-established tuning mechanism. The form factor, although reduced, in this case, depending on the dielectric loading, is better than what it is for a comparable reentrant cavity. We will present conceptual designs for cavities with different dielectric loadings that enable ADMX to search for axions in the range of 0.8-2.1 μeV. |
Tuesday, April 12, 2022 11:21AM - 11:33AM |
X07.00004: The ADMX Orpheus experiment: first results and future operations James Sinnis Orpheus is an axion haloscope using an open cavity design with dielectrics to search for axions with masses around 70 μeV. The axion is a hypothetical particle and an especially promising dark matter candidate. While it was predicted as a consequence of a solution to the strong CP problem, it could have been created in sufficient quantities in the early universe to solve the dark matter problem. Currently, the most sensitive axion haloscope, ADMX, uses a closed resonant cavity with a tunable frequency to couple to axions with masses of order 1 μeV (f0~1 GHz). However, higher order modes of standard closed cavity haloscopes do not couple strongly to the axion. They therefore require smaller cavity volumes for detecting axions at higher frequencies, significantly decreasing sensitivity. Orpheus modifies higher order modes to couple to the axion, and is thus able to explore higher frequencies and axion masses. As with any axion haloscope, data from Orpheus can also be used to search for dark photons, another dark matter candidate. In this talk, I will give an overview of the design and construction of Orpheus and present results from a dark photon search conducted in 2021. Finally, I will outline plans for Orpheus in 2022, when we expect to conduct our first axion search. |
Tuesday, April 12, 2022 11:33AM - 11:45AM |
X07.00005: The ORGAN Experiment: Phase1a Status and Results Aaron Quiskamp, Michael E Tobar, Ben T McAllister Precise cosmological measurements provide strong evidence for the existence of dark matter, and estimate that it accounts for 85% of all the matter in our Universe. Axions are hypothetical, massive, spin-0 particles that were first postulated as an elegant solution to the strong CP problem in quantum chromodynamics. The weakly interacting nature of axions simultaneously make them a popular dark matter candidate which can be searched for in experiments known as “haloscopes”, which exploit a putative axion-photon coupling. We present experimental details and initial results for Phase 1a of the Oscillating Resonant Group AxioN (ORGAN) experiment, a microwave cavity axion haloscope exploring the highly motivated ~ 60 - 200 μeV region of axion mass parameter space, corresponding to 15 - 50 GHz photons. Phase 1a scans for axion masses in the 15-16 GHz region of axion-photon coupling parameter space using a tunable TM010 conducting-rod resonator. This initial phase of ORGAN is set to be the most sensitive experiment in this region, achieving ALP-cogenesis sensitivity. Subsequent stages of ORGAN will utilise the Phase 1a infrastructure as a test bed for various technologies and techniques, such as GHz single photon counting, and novel cavity designs to explore the full 15-50 GHz range. |
Tuesday, April 12, 2022 11:45AM - 11:57AM |
X07.00006: CASPEr-Electric: second generation of low frequency search for axion-like dark matter using magnetic resonance Janos Adam, Glenn Randall, Andrew Winter, Alex O Sushkov Axions were originally proposed to solve the strong CP problem but they have become one of the most promising candidates for dark matter as well. We present the latest results of the second generation of the CASPEr-Electric experiment which searches for ultralight axion-like dark matter in the neV mass range (below 1 MHz). The experiment is sensitive to the interaction of axions with nuclear spins: the axion dark matter field creates an oscillating electric dipole moment of a 207Pb nucleus in a PMN-PT ferroelectric crystal. This dipole moment gives rise to a torque on the nuclear spin, and the resulting transverse nuclear magnetization can be detected with a superconducting quantum interference device (SQUID). We calibrate the sensitivity of the experiment by solid-state magnetic resonance on 207Pb nuclei and detect the signal with a SQUID. |
Tuesday, April 12, 2022 11:57AM - 12:09PM |
X07.00007: Sensitivity of Low-Mass and Resonant Axion Haloscopes using Poynting Theorem Michael E Tobar, Maxim Goryachev, Ben T McAllister The most sensitive haloscopes that search for axion dark matter through the two-photon electromagnetic anomaly, convert axions into photons through the mixing of axions with a large background DC magnetic field. In this work we apply Poynting theorem to the resulting axion modified electrodynamics and identify two possible Poynting vectors, one which is like the Abraham Poynting vector in electrodynamics and the other to the Minkowski Poynting vector [1]. The former is consistent with a zero total derivative and assume all surface effects go to zero in the low-mass limit, while the latter identifies additional surfaces, which contribute non-conservative terms to the sensitivity. We apply both Poynting theorems to both DC and AC haloscopes. We find that both Poynting theorems calculating the same sensitivity for a resonant DC haloscope. In contrast, there is a large difference in sensitivity calculations in the low mass when the Compton wavelength of the axion is much larger than the experimental dimensions for both the AC and DC haloscopes. We show low-mass haloscopes based on the Minkowski Poynting theorem predict orders of magnitude better sensitivity than those based on the Abraham Poynting theorem. Based on this work, we calculate the sensitivity of new low-mass haloscope topologies under investigation at the University of Western Australia [2,3]. |
Tuesday, April 12, 2022 12:09PM - 12:21PM |
X07.00008: Assessing the quality of a network of vector-field sensors Joseph A Smiga An experiment consisting of a network of sensors can endow several advantages over an experiment with a single sensor: improved sensitivity, error corrections, spatial resolution, etc. However, there is often a question of how to optimally set up the network to yield the best results. Here, we consider a network of devices that measure a vector field along a given axis; namely for magnetometers in the Global Network of Optical Magnetometers for Exotic physics searches (GNOME). We quantify how well the network is arranged, explore characteristics and examples of ideal networks, and characterize the optimal configuration for GNOME. We find that by re-orienting the sensitive axes of existing magnetometers, the sensitivity of the network can be improved by around a factor of two. |
Tuesday, April 12, 2022 12:21PM - 12:33PM |
X07.00009: A Model-Independent Radio Telescope Dark Matter Search Aya Keller, Sean O'Brien, Adyant M Kamdar, Nicholas M Rapidis, Alexander F Leder, Karl A van Bibber While significant attention has been paid to a few specific dark matter candidates such as the WIMP and axion, in fact the nature and mass of dark matter is poorly constrained, and thus a broad observational strategy may prove helpful toward its ultimate identification. We have developed and carried out a novel search technique for ultralight dark matter over a narrow range in L-band, utilizing the recent Breakthrough Listen public data release of three years of observation with the Green Bank Telescope. The search concept depends only on the assumption of decay or annihilation of virialized dark matter to a quasi-monochromatic radio line, and additionally that the frequency and intensity of the line be consistent with most general properties expected of the phase space of our Milky Way halo. Specifically, the search selects for a line which exhibits a Doppler shift with position according to the solar motion through a static galactic halo, and similarly varies in intensity with position with respect to the galactic center. Over the frequency range 1.73-1.83 GHz, radiative annihilation of dark matter is excluded above〈σv〉 = 1.2 x 10-47 cm3 s-1, and for decay above λ = 4.1 x 10-35 s-1. The analysis of the full L-, S-, C- and X-band dataset by this method (25,000 spectra, 1.1-11.6 GHz) is currently underway. |
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