An improved limit on the axion-photon coupling from the CAST experiment

We have searched for solar axions or similar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) set-up with improved conditions in all detectors. From the absence of excess x-rays when the magnet was pointing to the Sun, we set an upper limit on the axion-photon coupling of g(a gamma) < 8.8 x 10(-11) GeV-1 at 95% CL for m(a) less than or similar to 0.02 eV. This result is the best experimental limit over a broad range of axion masses and for m(a) less than or similar to 0.02 eV also supersedes the previous limit derived from energy-loss arguments on globular cluster stars.