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$\text{DMRadio-}{\mathrm{m}}^3$is an experimental search for dark matter axions. It uses a solenoidal dc magnetic field to convert an axion dark-matter signal to an ac electromagnetic response in a coaxial copper pickup. The current induced by this axion signal is measured by dc SQUIDs. $\text{DMRadio-}{\mathrm{m}}^3$is designed to be sensitive to Kim-Shifman-Vainshtein-Zakharov (KSVZ) and Dine-Fischler-Srednicki-Zhitnisky (DFSZ) QCD axion models in the 10–200 MHz ( $41\mathrm{neV}/c^2–0.83\mathrm{\mu }\mathrm{eV}/c^2$) range, and to axions with $g_{a\gamma \gamma }=g_{a\gamma \gamma ,\mathrm{DFSZ}}\left(30\mathrm{MHz}\right)=1.87\times {10}^{-17}{\mathrm{GeV}}^{-1}$over 5–30 MHz as an extended goal. In this work, we present the electromagnetic modeling of the response of the experiment to an axion signal over the full frequency range of $\text{DMRadio-}{\mathrm{m}}^3$, which extends from the low-frequency, lumped-element limit to a regime where the axion Compton wavelength is only a factor of 2 larger than the detector size. With these results, we determine the live time and sensitivity of the experiment. The primary science goal of sensitivity to DFSZ axions across 30–200 MHz can be achieved with a $3\sigma$live scan time of 2.9 years. 

This Letter reports new results from the HAYSTAC experiment’s search for dark matter axions in our galactic halo. It represents the widest search to date that utilizes squeezing to realize subquantum limited noise. The new results cover $1.71\mathrm{\mu }\mathrm{eV}$of newly scanned parameter space in the mass ranges $17.28–18.44\mathrm{\mu }\mathrm{eV}$and $18.71–19.46\mathrm{\mu }\mathrm{eV}$. No statistically significant evidence of an axion signal was observed, excluding couplings $\left|g_{\gamma }\right|\ge 2.75\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$and $\left|g_{\gamma }\right|\ge 2.96\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level over the respective region. By combining this data with previously published results using HAYSTAC’s squeezed state receiver, a total of $2.27\mathrm{\mu }\mathrm{eV}$of parameter space has now been scanned between $16.96–19.46\mathrm{\mu }\mathrm{eV}$ $\mu \mathrm{eV}$, excluding $\left|g_{\gamma }\right|\ge 2.86\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level. These results demonstrate the squeezed state receiver’s ability to probe axion models over a significant mass range while achieving a scan rate enhancement relative to a quantum-limited experiment. Published by the American Physical Society2025