The researchers propose a simple LSthinW (Light Shining Through a Thin Wall) setup that searches for hidden photons with masses of up to 1 eV using high-quality superconducting radio frequency (SRF) cavities. The LSthinW setup is unique in that it can generate and detect particles with masses of up to 0.1 eV, regardless of whether they are dark matter in our universe. This feature makes it a compelling option for experimental searches, especially since it may exceed the reach of certain dark matter detectors, despite the latter benefiting from the assumed presence of a hidden photon dark matter background.
One of the key aspects of the proposed setup is the use of thin superconducting barriers, which have a small penetration depth. This means that only several microns of shielding are required to sufficiently shield against hidden photons. The researchers focus on the evanescent regime, where the hidden photon is off-shell and the interaction occurs in the near-field region. The LSthinW setup could potentially enlarge the mass reach for related experiments searching for different types of particles, such as electromagnetically coupled axions and millicharged particles.
The researchers review the classical equations of motion governing SM and hidden photon fields, the production of hidden photons, and their excitation of EM cavities. They also use the formalism of Ref.  to compute field propagation across a conducting barrier. The researchers note that the mass suppression of the signal power in Eq is not fundamental, but results from the vanishing of the receiver cavity mode near the conducting barrier.
The proposed LSthinW experiment could be realized, but dedicated design efforts are needed to fully bring this proposal to light. The researchers recommend using electromagnetic cavities to conduct the experiment. However, searching for more massive hidden photons would require operating EM sources at higher frequencies, since this increases the maximum mass for which such particles can propagate on-shell. This is the strategy employed in current experiments such as ALPS and recently proposed millimeter wavelength setups.
Finally, the proposed LSthinW setup offers a promising path for searching for hidden photons. It is a novel approach that could potentially outperform certain dark matter detectors. Regardless of whether they are dark matter from our universe, particles with masses up to 0.1 eV may be detectable using thin superconducting barriers and excellent SRF cavities. The LSthinW experiment has the potential to produce ground-breaking findings in particle physics with careful design work.