Search for Dark Matter Axions with CAST-CAPP

TL;DR

This paper reports on a search for dark matter axions using the CAST-CAPP haloscope at CERN, setting new limits on axion-photon coupling in the 19.74 to 22.47 μeV mass range based on 4124 hours of data.

Contribution

It introduces a phase-matched resonator array in a dipole magnet for axion detection and reports the first results excluding certain axion-photon couplings in this mass range.

Findings

Excluded axion-photon couplings down to 8 x 10^{-14} GeV^{-1} at 90% CL.

Operated with four cavities over 4124 hours, tuning frequency from 4.774 to 5.434 GHz.

Demonstrated phase-matching technique for future large-scale axion searches.

Abstract

The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in the 19.74 $\mu$eV to 22.47 $\mu$eV mass range. The detection concept follows the Sikivie haloscope principle, where Dark Matter axions convert into photons within a resonator immersed in a magnetic field. The CAST-CAPP resonator is an array of four individual rectangular cavities inserted in a strong dipole magnet, phase-matched to maximize the detection sensitivity. Here we report on the data acquired for 4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning mechanism of 10 MHz/min between 4.774 GHz and 5.434 GHz. In the present work, we exclude axion-photon couplings for virialized galactic axions down to $g_{a{\gamma}{\gamma}} = 8 \times {10^{-14}}$ $GeV^{-1}$ at the 90% confidence level. The here implemented phase-matching technique also allows for future large-scale upgrades.