Near-Quantum-Noise Axion Dark Matter Search at CAPP around <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:mn>9.5</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi mathvariant="normal">μ</mml:mi></mml:mrow><mml:mi>eV</mml:mi></mml:mrow></mml:math>
Jinsu Kim, Ohjoon Kwon, Çağlar Kutlu, Woohyun Chung, Andrei Matlashov, S. Uchaikin, Arjan F. van Loo, Yasunobu Nakamura, Seonjeong Oh, HeeSu Byun, Danho Ahn, Yannis K. Semertzidis
Abstract
We report the results of an axion dark matter search over an axion mass range of 9.39-9.51 μeV. A flux-driven Josephson parametric amplifier (JPA) was added to the cryogenic receiver chain. A system noise temperature of as low as 200 mK was achieved, which is the lowest recorded noise among published axion cavity experiments with phase-insensitive JPA operation. In addition, we developed a two-stage scanning method which boosted the scan speed by 26%. As a result, a range of two-photon coupling in a plausible model for the QCD axion was excluded with an order of magnitude higher in sensitivity than existing limits.