First Results from the Taiwan Axion Search Experiment with Haloscope at 19.6 $\mu$eV

TL;DR

This paper reports the initial results of the Taiwan Axion Search Experiment using a microwave cavity, setting new limits on axion-photon coupling in the 19.5 μeV mass range, and demonstrating the experiment's sensitivity.

Contribution

First haloscope experiment to constrain axion-photon coupling at this mass range, improving existing limits by three orders of magnitude.

Findings

No axion candidates detected above significance threshold.

Excluded axion models with coupling above 8.2×10⁻¹⁴ GeV⁻¹ in the specified mass range.

Established new experimental constraints on axions in the 19.5 μeV mass region.

Abstract

This Letter reports on the first results from the Taiwan Axion Search Experiment with Haloscope, a search for axions using a microwave cavity at frequencies between 4.70750 and 4.79815 GHz. Apart from the non-axion signals, no candidates with a significance more than 3.355 were found. The experiment excludes models with the axion-two-photon coupling $\left|g_{a\gamma\gamma}\right|\gtrsim 8.2\times 10^{-14}$ GeV$^{-1}$, a factor of eleven above the benchmark KSVZ model, reaching a sensitivity three orders of magnitude better than any existing limits in the mass range 19.4687 < $m_a$ < 19.8436 $\mu$eV. It is also the first time that a haloscope-type experiment places constraints on $g_{a\gamma\gamma}$ in this mass region.