Mitsuyoshi Tanaka Dissertation Award Talk: First results from the HAYSTAC axion search

Hypothetical particles called axions are among the leading candidates for the mysterious cold dark matter (CDM) that binds galaxies together and constitutes more than 80% of the matter in the universe. CDM axions may be detected via their resonant conversion into photons in a "haloscope" detector: a tunable, high-$Q$ microwave cavity maintained at cryogenic temperature, immersed a strong magnetic field, and coupled to a low-noise receiver. At the limits of current technology, the conversion power in such a detector is $\lesssim 10^{-22}\mathrm{ W}$ for $\mu\mathrm{eV}$-mass axions, and drops rapidly with increasing axion mass, because higher frequency cavities with smaller resonant volumes are required. In this talk I will introduce the essential physics of CDM axion detection, and review the main results of my doctoral research with HAYSTAC (the Haloscope at Yale Sensitive to Axion CDM), for which I received the 2019 Tanaka award. HAYSTAC is the first detector to achieve sensitivity to viable axion models in the $10\mathrm{ }\mu\mathrm{eV}$ mass decade, and the first to demonstrate noise performance limited by the laws of quantum mechanics. I will end the talk with a brief preview of next steps for HAYSTAC specifically and a broader outlook for the field of light dark matter detection.