Axion astronomy with microwave cavity experiments

Abstract

Terrestrial searches for the conversion of dark matter axions or axion-like particles into photons inside magnetic fields are sensitive to the phase space structure of the local Milky Way halo. We simulate signals in a hypothetical future experiment based on the Axion Dark Matter eXperiment (ADMX) that could be performed once the axion has been detected and a frequency range containing the axion mass has been identified. We develop a statistical analysis to extract astrophysical parameters, such as the halo velocity dispersion and laboratory velocity, from such data and find that with only a few days integration time a level of precision can be reached matching that of astronomical observations. For longer experiments lasting up to a year in duration we find that exploiting the modulation of the power spectrum in time allows accurate measurements of the Solar peculiar velocity with an accuracy that would improve upon astronomical observations. We also simulate signals based on results from N-body simulations and find that finer substructure in the form of tidal streams would show up prominently in future data, even if only a subdominant contribution to the local dark matter distribution. In these cases it would be possible to reconstruct all the properties of a dark matter stream using the time and frequency dependence of the signal. Finally we consider the detection prospects for a network of streams from tidally disrupted axion miniclusters. These features appear much more prominently in the resolved spectrum than suggested by calculations based on a scan over a range of resonant frequencies, making the detection of axion minicluster streams more viable than previously thought. These results confirm that haloscope experiments in a post-discovery era are able to perform "axion astronomy".

Refinement of the standard halo model for dark matter searches in light of the Gaia Sausage

“…Hence it is not surprising that the refinements that we have made have little impact on limits on the axion-photon coupling. As has been discussed in the past, the only changes that can bring significant changes to the axion signal are cold substructures like streams, which present highly localised peaks in frequency [12,20,21,133]. One exception may be directional axion experiments possessing sensitivity to the full velocity distribution via prominent diurnal modulations [12,193].…”

Velocity substructure from Gaia and direct searches for dark matter

“…For most of the haloscope techniques discussed, the spectral density of axion-induced photons is proportional to the speed distribution, up to a change of variables between frequency and speed (see e.g., Refs. [37,137])…”

Searching for the QCD Axion with Gravitational Microlensing

“…If axions are ever detected directly in the lab, then tidal stripping of miniclusters allows f MC to be measured from the phase-space distribution [36,43]. Independently of f MC , axions in the mass range accessible to microlensing can be detected via the force they mediate using the proposed experiment "ARIADNE" [49].…”

“…Equation (4) defines the NFW characteristic density ρðrÞ ¼ ρ c =½ðr=r s Þ ð1 þ r=r s Þ 2 , with the scale radius defined from ρ c after fixing the total mass M of the minicluster/MCH and assuming the profiles extends to 100 r s . An alternative minicluster/MCH density profile fixes ρ c as the core density and the radial dependence as r −9=4 from self-similar infall [43] and is explored in Ref. [22].…”