Axion Dark Matter: How to see it?

Abstract

The axion, originated from the Peccei-Quinn mechanism proposed to solve the strong-CP problem, is a well motivated and popular dark matter candidate. Experimental searches for this hypothetical particle are starting to reach theoretically interesting sensitivity levels. However, only a small fraction of the allowed parameter space has been explored so far, mostly in the µeV (GHz) region, relying on large volume solenoid magnetic fields and microwave resonators with signals read out by quantum noise limited amplifiers. There have been intensive experimental efforts to widen the search range by devising various techniques as well as to enhance sensitivities by implementing advanced technologies. The developments and improvements in these orthogonal approaches will enable us to explore most of the parameter space of the axion and axion-like particles within the next five to ten years. We review the experimental aspects of axion physics and discuss the past, present and future of the individual search programs.

Interaction of inhomogeneous axions with magnetic fields in the early universe

“…Thus, we take f a = 10 12 GeV since we have chosen m = 10 −6 eV. The suggested values of m and f a are in the sensitivity range of the operating and future lumped element detectors [8] (see also Refs. [20,21]).…”

Axion emission from supernova with axion-pion-nucleon contact interaction

“…After recognizing that axions provide a compelling candidate for the dark matter in the Universe [8][9][10], a lot of efforts have been made to search for axions over the parameter space of the representative axion models [11][12][13][14]. Since the viable parameter region is in the very weakly coupled regime, most of the laboratory experiments searching for axions are ongoing in the direction of the precision measurements using, for example, resonant cavities, nuclear magnetic resonance, light shining through the walls, and polarization of lights in magnetic fields (see [15][16][17] for comprehensive reviews).…”

Relativistic spin dynamics conditioned by dark matter axions

“…This effect is observable and axions are searched in experiments with haloscopes. We can mention the experiments ADMX [15], ADMX-HF [16], HAYSTAC [17], CAPP [18,19], and RADES [20] and the reviews [9,10,12,[21][22][23][24]. We can also note experiments with helioscopes (see, e.g.,…”