DFSZ Axion Dark Matter Search around 4.5 μeV at IBS-CAPP

The axion is a well-motivated particle that provides a solution to the strong CP problem and is also a candidate for cold dark matter. The CAPP-12TB experiment is the flagship axion dark matter experiment at the Center for Axion and Precision Physics Research (CAPP). The system features a superconducting solenoid with a bore size of 320 mm and a maximum central field of 12 T, a cryogenic dilution fridge with physical temperatures around 30 mK with cavity load. Nearly quantum-noise-limited flux-driven Josephson parametric amplifiers are utilized as the first amplifier of the receiver chain. The experiment uses a copper microwave cavity that has a large volume (37 L) and an unloaded Q-factor around 100,000 along its frequency range tuned by a copper rod. We report the first results of the experiment which excludes the Dine-Fischler-Srednicki-Zhitnitskii (DFSZ) axion model for the mass range 4.38 μeV (1.06 GHz) to 4.63 μeV (1.12 GHz) at a 90% confidence level. The CAPP-12TB experiment will continue its search for DFSZ axions over a wider range of axion masses using a series of new cavities and receiver chains.