CAST solar axion search with 3He buffer gas: Closing the hot dark matter gap
Abstract
The CERN Axion Solar Telescope (CAST) has finished its search for solar axions with 3He buffer gas, covering the search range 0.64 eV < ma <1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gag < 3.3 x 10-10 GeV-1 at 95% CL, with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of ga, for example by the currently discussed next generation helioscope IAXO.
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