First Results from the Taiwan Axion Search Experiment with a Haloscope at 19.6 μeV

PHYSICAL REVIEW LETTERS

Hsin Chang, Jing-Yang Chang, Yi-Chieh Chang, Yu-Han Chang, Yuan-Hann Chang, Chien-Han Chen, Ching-Fang Chen, Kuan-Yu Chen, Yung-Fu Chen, Wei-Yuan Chiang, Wei-Chen Chien, Hien Thi Doan, Wei-Cheng Hung, Watson Kuo, Shou-Bai Lai, Han-Wen Liu, Min-Wei OuYang, Ping-I Wu, and Shin-Shan Yu (TASEH Collaboration)

First Results from the Taiwan Axion Search Experiment with a Haloscope at 19.6 μ eV

軸子為熱門的暗物質候選人之一。在外加強磁場的影響之下，軸子有機會轉換成光子。如果偵測器裡的微波共振腔共振頻率對應到了光子頻率，經過低噪放大器的放大信號，我們有機會探測到軸子的存在。台灣軸子偵測實驗室(TASEH)用在2021年10月13日至11月15日所取的數據，尋找了軸子暗物質。我們的結果排除了軸子-雙光子耦合常數大於8.1 x 10-14 GeV-1的理論模型。在19.4687 至19.7639微電子伏特這個質量範圍，我們對理論模型的敏感度比之前實驗還要好三個數量級。

One of the viable dark matter candidates is the axion. An axion in an external magnetic field can convert to an equal-energy photon. The converted photons can be accumulated in a cavity with a matched resonant frequency and subsequently be detected by a low-noise linear amplifier. The Taiwan Axion Search Experiment with a Haloscope (TASEH) has performed a search for axions, using the data collected from October 13, 2021 to November 15, 2021. The results of TASEH excludes models with the axion-two-photon coupling |gaγγ|8.1 x 10-14 GeV-1. It is the first time that a haloscope experiment places constraints in the mass region of 19.4687 < ma < 19.7639 μeV, reaching a sensitivity 3 orders of magnitude better than the limits obtained by nonhaloscope experiments.

The simplified diagram of the TASEH apparatus
(a) The schematic diagram of the TASEH cryogen-free dilution refrigerator system, (b) An overview photo of the TASEH experimental setup.

The 95% CL limits on |gaγγ| and the ratio of the average limit with respect to the KSVZ benchmark value from the CD102 data
(red band in the inset). The results from the previous searches performed by the ADMX, CAPP, CAST HAYSTAC, RBF, and UF Collaborations are also shown (inset). The blue error band indicates the systematic uncertainties. The gray band in the inset shows the allowed region of |gaγγ| vs axion mass from various QCD axion models, while the blue and red dashed lines are the values predicted by the KSVZ and DFSZ benchmark models, respectively.