Search for Invisible Axion Dark Matter with the Axion Dark Matter Experiment

Abstract

This Letter reports the results from a haloscope search for dark matter axions with masses between 2.66 and 2.81 μeV. 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 subkelvin temperatures, thereby reducing thermal noise as well as the excess noise from the ultralow-noise superconducting quantum interference device 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. DOI: 10.1103/PhysRevLett.120.151301 Axions are particles predicted to exist as a consequence of the Peccei-Quinn solution to the strong-CP problem [1][2][3] and could account for all of the dark matter in our Universe [4][5][6]. While there exist a number of mechanisms to produce axions in the early Universe [4,[7][8][9] that allow for a wide range of dark matter axion masses, current numerical and analytical studies of QCD typically suggest a preferred mass range of 1-100 μeV for axions produced after cosmic inflation in numbers that saturate the Lambda-CDM (cold dark matter) density [10][11][12][13][14]. The predicted coupling between axions and photons is model dependent; in general, axions with dominant hadronic couplings as in the Kim-Shifman-Vainshtein-Zakharov (KSVZ) model [15,16] are predicted to have an axion-photon coupling roughly 2.7 times larger than that of the Dine-FischlerSrednicki-Zhitnitsky (DFSZ) model [17,18]. Because the axion-photon coupling is expected to be very small, Oð10 −17 -10 −12 GeV −1 Þ over the expected axion mass range, these predicted particles are dubbed invisible axions [4].The most promising technique to search for dark matter axions in the favored mass range is the axion haloscope [19] consisting of a cold microwave resonator immersed in a strong static magnetic field. In the presence of this magnetic field, the ambient dark matter axion field produces a volume-filling current density oscillating at frequency f ¼ E=h, where E is the total energy consisting mostly of the axion rest mass with a small kinetic energy addition. When the resonator is tuned to match this frequency, the current source delivers power to the resonator in the form of microwave photons which can be detected with a low-noise microwave receiver. To date, a number of axion haloscopes have been implemented. All had noise levels too high to detect the QCD axion signal [20][21][22][23][24][25][26][27][28][29][30] in an experimentally realizable time. Previous versions of the Axion Dark Matter eXperiment (ADMX) [24][25][26][27][28][29] achieved sensitivity to the stronger KSVZ couplings in the ð1.91-3.69Þ-μeV mass range. ADMX has since been improved to utilize a dilution refrigerator to obtain a significantly lower system noise temperature, drastically increasing its sensitivity. We present here results from the first axion experiment to have sensitivity to the more weakly coupled DFSZ axion ...

Large-misalignment mechanism for the formation of compact axion structures: Signatures from the QCD axion to fuzzy dark matter

“…where we have taken v rel = 10 −3 for definiteness. For completeness, we note that this corresponds to a FH scale radius: 11 The most notable axion experiment that falls in this category is ADMX [139]. We also refer the reader to the Particle Data Group review of axions [140] for a summary of other proposed experiments that are relevant for our discussion.…”

Exploiting higher-order resonant modes for axion haloscopes

“…A conventional way to tune the resonant frequency of a cylindrical cavity is to break the transverse symmetry by translating a (pair of) dielectric or conducting rod(s) in the radial direction [7,8]. For a cylindrical dielectric cavity, such symmetry breaking can be achieved by splitting the dielectric hollow vertically into pieces and moving them apart along the radial direction.…”

Axiogenesis

“…We show how new physics at the 1-10 TeV scale can raise T ws so that the axion can constitute a subdominant or correct amount of dark matter. In addition to new heavy states, axiogenesis also favors a small decay constant which is accessible to many axion haloscope and helioscope experiments [74][75][76][77][78][79][80][81][82][83][84][85][86]. The evolution of the PQ breaking field reveals nonstandard cosmological eras, which alone may have profound implications for other aspects of cosmology.…”