The CAST experiment: status and perspectives

TL;DR

The CAST experiment searches for solar axions using a magnet and gas buffers, setting upper limits on axion-photon coupling and exploring higher mass ranges with ongoing and future phases.

Contribution

This paper reports on the status, recent results, and future perspectives of the CERN Axion Solar Telescope (CAST) experiment for solar axion detection.

Findings

Set an upper limit on axion-photon coupling of ~2.17×10^{-10} GeV^{-1} for axion masses below 0.4 eV.

Conducted a search for axions up to 1.2 eV using extsuperscript{3}He buffer gas.

Presented expectations for future sensitivity improvements and long-term experimental options.

Abstract

The status of the solar axion search with the CERN Axion Solar Telescope (CAST) will be discussed. Results from the first part of CAST phase II where the magnet bores were filled with \hefour gas at variable pressure in order to scan \ma up to 0.4 eV will be presented. 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 $\gag \lesssim 2.17 \times10^{-10}$GeV$^{-1}$ at 95% CL for \ma$<0.4$ eV, the exact result depending on the pressure setting. Our search for axions with masses up to about 1.2 eV using \hethree as a buffer gas is, since last year, in progress in the second part of CAST phase II. Expectations for sensibilities will be given. Near future perspectives as well as more long term options for a new helioscope experiment will be evoked.