First results from a microwave cavity axion search at $25~\mu\mathrm{eV}$: Overview*

The axion is a well-motivated cold dark matter candidate first postulated to explain the absence of CP violation in strong interactions. Dark matter axions may be detected via their resonant conversion into photons in a high-$Q$ microwave cavity permeated by a strong magnetic field. In this talk I will present an overview of a newly operational cavity detector at Yale, which is the first such detector to incorporate a dilution refrigerator and Josephson parametric amplifier and thereby approach quantum-limited noise performance. I will discuss the first results from this experiment, which has excluded axion models with two-photon coupling $g_{a\gamma\gamma} > 2\times10^{-14} \mathrm{GeV}^{-1}$, a factor of $\simeq2.3$ above the benchmark KSVZ model, over the mass range $23.55~\mu\mathrm{eV} < m_a < 24.0~\mu\mathrm{eV}$. These are the first limits within the axion model band in the $10~\mu\mathrm{eV}$ mass decade.