Axions: Recent searches and new limits
Abstract
Description
The CERN Axion Solar Telescope (CAST) experiment searches for solar axions by the "helioscope" method. First results imply an upper limit on the axion-photon coupling of g_a-gamma < 1.16 x 10^-10 GeV^-1 (95% CL) for m_a < 0.02 eV, in this mass range superseding the previous energy-loss limit from globular cluster stars. By virtue of a variable-pressure helium filling of the magnetic transition region, CAST II will extend the sensitivity to axion masses up to about 1 eV, for the first time testing realistic axion parameters in a laboratory experiment. In this mass range axions would contribute a cosmic hot dark matter component. New structure-formation limits imply that m_a < 1-2 eV. For the particular case of hadronic axions with a standard axion-pion coupling, the present-day cosmic axion density would be about 50 cm^-3 and the cosmic mass limit is m_a < 1.05 eV (95% CL). We also comment on the axion interpretation of the anomalous signature observed in the PVLAS experiment.
Contribution to XI International Workshop on "Neutrino Telescopes" (22-25 Feb 2005, Venice, Italy)
Contribution to XI International Workshop on "Neutrino Telescopes" (22-25 Feb 2005, Venice, Italy)