Experimental Constraints on the Axion Dark Matter Halo Density

Most of the mass of the Milky Way galaxy is contributed by its halo, presumably in the form of non-interacting cold dark matter. The axion is a compelling cold dark matter candidate. We report results from a search which probes the local galactic halo axion density using the Sikivie RF cavity technique. Candidates over the frequency range 550 ≤ f ≤ 810 MHz (2.3 µeV ≤ ma ≤ 3.4 µeV) were investigated. The absence of a signal suggests that KSVZ axions contribute no more than 0.45 GeV/cm 3 of mass density to the local dark matter halo over this mass range. Subject headings: dark matter–Galaxy: halo–instrumentation: detectors