Recent Results from the Tokyo Axion Helioscope Experiment

We have searched for axions which could have been produced in the solar core using an axion helioscope which is equipped with a 2.3 m-long 4 T superconducting magnet , PIN-photodiode x-ray detectors, and a telescope mount mechanism to track the sun. A gas container to hold dispersion-matching gas has been developed and a mass region up to ma = 0.26 eV was newly explored. Preliminary analysis sets a limit on axion-photon coupling constant to be gaγγ < 6.4 ∼ 9.6 × 10 −10 GeV −1 for the axion mass of 0.05 < ma < 0.26 eV at 95% confidence level from the absence of the axion signal. This is more stringent than the limit inferred from the solar age consideration and also more stringent than the recent helioseismological bound.