We report on a new search for solar chameleons with the CERN Axion Solar
Telescope (CAST). A GridPix detector was used to search for soft X-ray
photons in the energy range from 200 eV to 10 keV from converted solar
chameleons. No significant excess over the expected background has been
observed in the data taken in 2014 and 2015. We set an improved limit on
the chameleon photon coupling, βγ#5.7×1010 for 1<βm<106
at 95% C.L. improving our previous results by a factor two and for the
first time reaching sensitivity below the solar luminosity bound for
tachocline magnetic fields up to 12.5 T.
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- Dark energy experiments
- Modified gravity
- Particle physics - cosmology connection
- Solar physics