Searching for Dark Photons and Axions with Two Superconducting RF Cavities: Light-Shining-Through-Wall Setups

Graham et al. proposed detecting dark photons with two identical SRF cavities [1]. This proposal, like other light-shining-through-wall (LSW) setups, is sensitive to dark photons with masses below the resonant frequency due to the long distance between the emitter and receiver cavities. Dark photons with masses larger than the resonant frequency decay exponentially with the Compton wavelength as they leave the emitter. Recently, the first LSW experiment for dark photons with two ultrahigh-Q superconducting radio-frequency (SRF) cavities was performed and established a new exclusion limit for kinetic mixing [2]. In addition, Gao and Harnik proposed a LSW setup with two SRF cavities for detecting the hypothetical axion [3]. This two cavity method for the axion detection is sensitive to axions with light masses due to a long distance between the emitter and receiver as well as that for the dark photon detection. Using these setups [1,3], we calculate sensitivity to dark photons and axions as a function of distance between the two cavities and examine the sensitivities of different cavity modes. We also discuss the leakage field from the emitter to the receiver for LSW setups with thin walls recently proposed by Berlin et al. [4].

[1] P. W. Graham et al., Phys. Rev. D 90, 075017 (2014). [2] A. Romanenko et al., Phys. Rev. Lett. 130, 261801 (2023). [3] C. Gao and R. Harnik, J. High Energ. Phys. 2021, 53 (2021). [4] A. Berlin, R. Harnik, and R. Janish, arXiv.2303.00014.