Yang Byeongsu, Yoon Hojin, Ahn Moohyun, Lee Youngjae, Yoo Jonghee
Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea.
Phys Rev Lett. 2023 Aug 25;131(8):081801. doi: 10.1103/PhysRevLett.131.081801.
We report an extended search for the axion dark matter using the CAPP18T haloscope. The CAPP18T experiment adopts innovative technologies of a high-temperature superconducting magnet and a Josephson parametric converter. The CAPP18T detector was reconstructed after an unexpected incident of the high-temperature superconducting magnet quenching. The system reconstruction includes rebuilding the magnet, improving the impedance matching in the microwave chain, and mechanically readjusting the tuning rod to the cavity for improved thermal contact. The total system noise temperature is ∼0.6 K. The coupling between the cavity and the strong antenna is maintained at β≃2 to enhance the axion search scanning speed. The scan frequency range is from 4.8077 to 4.8181 GHz. No significant indication of the axion dark matter signature is observed. The results set the best upper bound of the axion-photon-photon coupling (g_{aγγ}) in the mass ranges of 19.883 to 19.926 μeV at ∼0.7×|g_{aγγ}^{KSVZ}| or ∼1.9×|g_{aγγ}^{DFSZ}| with 90% confidence level. The results demonstrate that a reliable search of the high-mass dark matter axions can be achieved beyond the benchmark models using the technology adopted in CAPP18T.
我们报告了使用CAPP18T轴子暗物质探测仪进行的扩展搜索。CAPP18T实验采用了高温超导磁体和约瑟夫森参量转换器等创新技术。在高温超导磁体发生意外失超事件后，对CAPP18T探测器进行了重建。系统重建包括重建磁体、改善微波链路中的阻抗匹配以及对调谐杆与腔体进行机械调整以改善热接触。整个系统的噪声温度约为0.6 K。将腔体与强天线之间的耦合保持在β≃2，以提高轴子搜索的扫描速度。扫描频率范围为4.8077至4.8181 GHz。未观察到轴子暗物质特征的明显迹象。结果在19.883至19.926 μeV的质量范围内，以90%的置信水平设定了轴子 - 光子 - 光子耦合（g_{aγγ}）的最佳上限，约为0.7×|g_{aγγ}^{KSVZ}|或约1.9×|g_{aγγ}^{DFSZ}|。结果表明，使用CAPP18T采用的技术，可以在基准模型之外实现对高质量暗物质轴子的可靠搜索。
