First results from the CERN Axion Solar Telescope (CAST)

TL;DR

This paper reports initial results from the CERN Axion Solar Telescope, which searches for axion-like particles produced in the Sun, setting new upper limits on their coupling to photons in a specific mass range.

Contribution

First experimental results from CAST using a decommissioned LHC magnet, providing the most restrictive limits to date on axion-photon coupling for certain masses.

Findings

No axion signal detected above background.

Set an upper limit on axion-photon coupling < 1.16 x 10^{-10} GeV^{-1}.

Limit is comparable or better than previous astrophysical constraints.

Abstract

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 has been running 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 < 1.16 10^{-10} GeV^-1 at 95% CL for m_a <~0.02 eV. This limit is comparable to the limit from stellar energy-loss arguments and considerably more restrictive than any previous experiment in this axion mass range.