Hypothetical axion-like particles with a two-photon interaction would be produced in the Sun by the Primakoff process .
In a laboratory magnetic field ( “ axion helioscope ” ) they would be transformed into X-rays with energies of a few keV .
Using a decommissioned LHC test magnet , CAST ran for about 6 months during 2003 .
The first results from the analysis of these data are presented here .
No signal above background was observed , implying an upper limit to the axion-photon coupling g _ { a \gamma } < 1.16 \times 10 ^ { -10 } ~ { } { GeV } ^ { -1 } at 95 % CL for m _ { a } \lesssim 0.02 ~ { } { eV } .
This limit , assumption-free , is comparable to the limit from stellar energy-loss arguments and considerably more restrictive than any previous experiment over a broad range of axion masses .