Search for invisible axion dark matter of mass m${}_a=43\hat{I}¼$eV with the QUAX--$a{\hat{I}}^3$ experiment

Abstract

A haloscope of the QUAX--$a{\hat{I}}^3$ experiment composed of an oxygen-free high thermal conductivity-Cu cavity inside an 8.1 T magnet and cooled to $\sim 200$ mK is put in operation for the search of galactic axion with mass $m_a\simeq 43\hat{I}¼\text{eV}$. The power emitted by the resonant cavity is amplified with a Josephson parametric amplifier whose noise fluctuations are at the standard quantum limit. With the data collected in about 1 h at the cavity frequency $\hat{I}{½}_c=10.40176$ GHz, the experiment reaches the sensitivity necessary for the detection of galactic QCD-axion, setting the $90\%$ confidence level limit to the axion-photon coupling $g_{a{\hat{I}}^3{\hat{I}}^3}<0.639\times 10^{-13}$ GeV${}^{-1}$.

7 pages, 6 figures. Analysis method changed. The result is almost left unchanged. Consequently, text has been revised in the Analysis section. Added references. Added equations (2), (4), (5)