Experimental Constraints on the Axion Dark Matter Halo Density

Most of the mass of the Milky Way is contributed by its halo, presumably in the form of noninteracting cold dark matter. The axion is a compelling cold dark matter candidate. We report results from a search that probes the local Galactic halo axion density using the Sikivie radio frequency cavity technique. Candidates over the frequency range 550 MHz ≤ f ≤ 810 MHz (2.3 μeV ≤ ma ≤ 3.4 μeV) were investigated. The absence of a signal suggests that the axions of Kim and Shifman, Vainshtein, & Zakharov contribute no more than 0.45 GeV cm-3 of mass density to the local dark matter halo over this mass range.