Projected Sensitivity of DMRadio-m\(^3\): A Search for the QCD Axion Below \(1\,\mu\)eV

The QCD axion is one of the most compelling candidates to explain the dark matter abundance of the universe. With its extremely small mass (\(\ll 1\,\mathrm{eV}/c^2\)), axion dark matter interacts as a classical field rather than a particle. Its coupling to photons leads to a modification of Maxwell's equations that can be measured with extremely sensitive readout circuits. DMRadio-m\(^3\) is a next-generation search for axion dark matter below \(1\,\mu\)eV using a \(>4\) T static magnetic field, a coaxial inductive pickup, a tunable LC resonator, and a DC-SQUID readout. It is designed to search for QCD axion dark matter over the range \(20\,\mathrm{neV}\lesssim m_ac^2\lesssim 800\,\mathrm{neV}\) (\(5\,\mathrm{MHz}