Extensive Search for Axion Dark Matter over 1 GHz with CAPP’S Main Axion Experiment
Saebyeok Ahn, JinMyeong Kim, B. I. Ivanov, Ohjoon Kwon, HeeSu Byun, Arjan F. van Loo, SeongTae Park, J. H. Jeong, Soohyung Lee, Jinsu Kim, Çağlar Kutlu, Andrew K. Yi, Yasunobu Nakamura, Seonjeong Oh, Danho Ahn, Sungjae Bae, Hyoungsoon Choi, Jihoon Choi, Yonuk Chong, Woohyun Chung, Violeta Gkika, Jihn E. Kim, Young-Geun Kim, B. R. Ko, L. Miceli, Doyu Lee, Jiwon Lee, Ki Woong Lee, M. J. Lee, Andrei Matlashov, Pallavi Parashar, Taehyeon Seong, Yun Chang Shin, S. Uchaikin, SungWoo Youn, Yannis K. Semertzidis
Abstract
We report an extensive high-sensitivity search for axion dark matter above 1 GHz at the Center for Axion and Precision Physics Research (CAPP). The cavity resonant search, exploiting the coupling between axions and photons, explored the frequency (mass) range of 1.025 GHz (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>4.24</a:mn><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi mathvariant="normal">μ</a:mi><a:mi>eV</a:mi></a:mrow></a:math>) to 1.185 GHz (<d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mrow><d:mn>4.91</d:mn><d:mtext> </d:mtext><d:mtext> </d:mtext><d:mi mathvariant="normal">μ</d:mi><d:mi>eV</d:mi></d:mrow></d:math>). We have introduced a number of innovations in this field, demonstrating the practical approach of optimizing all the relevant parameters of axion haloscopes, extending presently available technology. The CAPP 12 T magnet with an aperture of 320 mm made of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:msub><g:mrow><g:mi>Nb</g:mi></g:mrow><g:mrow><g:mn>3</g:mn></g:mrow></g:msub><g:mi>Sn</g:mi></g:mrow></g:math> and NbTi superconductors surrounding a 37 l ultralight-weight copper cavity is expected to convert Dine-Fischler-Srednicki-Zhitnitsky axions into approximately <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msup><i:mn>10</i:mn><i:mn>2</i:mn></i:msup></i:math> microwave photons per second. A powerful dilution refrigerator, capable of keeping the core system below 40 mK, combined with quantum-noise-limited readout electronics, achieved a total system noise of about 200 mK or below, which corresponds to a background of roughly <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mn>4</k:mn><k:mo>×</k:mo><k:msup><k:mn>10</k:mn><k:mn>3</k:mn></k:msup></k:math> photons per second within the axion bandwidth. The combination of all those improvements provides unprecedented search performance, imposing the most stringent exclusion limits on axion-photon coupling in this frequency range to date. These results also suggest an experimental capability suitable for highly sensitive searches for axion dark matter above 1 GHz. Published by the American Physical Society 2024