Results from a search for cosmic axions

Abstract

A search experiment has been carried out to look for relic cosmic axions trapped in the halo of our Galaxy and limits on their coupling gar, and galactic abundance are presented for the axion mass range of ma -( 5 . 4 -5 . 9 )~ eV. The detector consisted of a tunable high-Q microwave cavity immersed in liquid helium and permeated by a strong magnetic field. A low-noise microwave receiver with a cryogenic HEMT amplifier as its first stage was coupled to the cavity. The noise power within successive cavity bandwidths was spectrum analyzed and searched for narrow peaks resulting from axion-to-photon conversions in the cavity.

Searches for invisible axions

“…The other first-generation microwave cavity experiment was carried out at the University of Florida [7] The superconducting solenoid magnet (17 1 cm diameter, 40 cm length) produced a peak central field of 8.6 T The cavities, made of high purity oxygen-free copper, had an unloaded quality factor at 15GHzofQw-16 x 105, measured at 4 2 K physical temperature The operating temperature of the experiment was normally 2.2 K. Coarse tuning was done by a large dielectric rod moved transversely in the cavity, and fine tuning by insertion of a small tuning rod inserted through a hole in the top plate of the cavity.…”

“…Our many colleagues who assisted us in this review are unfortunately too numerous to acknowledge by name, but we are sincerely grateful for their help the University of Florida, [7] the US large-scale experiment, [8] and the Kyoto experiment. [g] The sensitivity possible for the large-scale experiment upgraded with DC SQUID amplifiers is indicated by the shaded dashed line All are normalized t?…”

“…In 1983, Pierre Sikivie of the University of Florida showed how halo dark matter axions could be detected by their Primakoff conversion to microwave photons in a high-Q resonator permeated by an intense magnetic field. [5] First-generation experiments at BNL [G] and the University of Florida [7] demonstrated the experimental technique, and laid the groundwork for second-generation efforts in the US [8] and Japan [9] of which the former has finally reached sensitivity to realistic axion models with best-fit local halo Cold Dark Matter (CDM) densities. Upgrades are being planned to further increase sensitivity and search rate, to maximize the chances of the discovery of the axion.…”

Electromagnetic detection of axions

“…where φ a is the axion field, m a its mass,F µν = 1 2 ε µνρσ F ρσ , and f a is the axion decay constant and is defined in terms of the axion mass m a by [5,9]: (1) is model dependent. Interaction of the axions to the photons arises from the triangle loop diagram, in which two vertices are interactions of the photon to electrically charged fermion and an another vertex is coupling of the axion with fermion.…”

“…For a = c = 1m, the intensity of the electric field E = 100kV m , and m a = 1eV [9] then the cross section is given by (11)…”