Search for invisible axion dark matter of mass ma=43 μeV with the QUAX–aγ experiment

A haloscope of the QUAX--$a\\ensuremath{\\gamma}$ experiment composed of an oxygen-free high thermal conductivity-Cu cavity inside an 8.1 T magnet and cooled to $\\ensuremath{\\sim}200\\text{ }\\text{ }\\mathrm{mK}$ is put in operation for the search of galactic axion with mass ${m}_{a}\\ensuremath{\\simeq}43\\text{ }\\text{ }\\ensuremath{\\mu}\\mathrm{eV}$. 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 ${\\ensuremath{\\nu}}_{c}=10.40176\\text{ }\\text{ }\\mathrm{GHz}$, the experiment reaches the sensitivity necessary for the detection of galactic QCD-axion, setting the 90% confidence level limit to the axion-photon coupling ${g}_{a\\ensuremath{\\gamma}\\ensuremath{\\gamma}}l0.766\\ifmmode\\times\\else\\texttimes\\fi{}{10}^{\\ensuremath{-}13}\\text{ }\\text{ }{\\mathrm{GeV}}^{\\ensuremath{-}1}$.