The Search for Axion
Dark Matter
The axion provides a
solution to the strong CP problem and is a cold dark matter candidate.
I'll review the limits on the axion from particle physics, stellar evolution
and cosmology. The various constraints suggest that the axion mass is in
the micro-eV to milli-eV range. In this window, axions contribute
significantly to the energy density of the universe in the form of cold dark
matter. Dark matter axions can be searched for on Earth by stimulating
their conversion to microwave photons in an electromagnetic cavity permeated by
a strong magnetic field. Using this technique, limits on the local halo
density have been placed by the Axion Dark Matter eXperiment at Lawrence
Livermore National Laboratory. I'll give a status report on ADMX and its
upgrade presently under construction.
I'll also discuss the results from solar axion searches and laser
experiments.