In Search Of Axions: The CAST Experiment

Abstract. The CERN Axion Solar Telescope (CAST) experiment uses a decommissioned LHC test magnet in conjunction with three different technology X-ray photon detectors and tracks the sun to look for the elusive axion. Axions or axion-like particles with a two-photon interaction can be produced in the Sun by the Primakoff process, according to the theory. In a laboratory magnetic field they can be transformed into X-rays with energies of a few keV. CAST has been running for about 6 months during 2003 and most of 2004. The first results from the analysis of the 2003 data are presented here. No signal above background was observed, implying an upper limit to the axion to photon coupling gαγγ < 1.16 × 10-10 GeV-1 at 95 % CL for mα ≤ 0.02 eV. This limit is comparable to the limit from stellar energy loss arguments and considerably more restrictive than any previous experiment in this axion mass range