Search for Dark Photon Dark Matter in the Mass Range 41--74 $\mu \mathrm{e}\mathrm{V}$ using Millimeter-Wave Receiver and Radioshielding Box

Dark photons have been considered potential candidates for dark matter. The dark photon dark matter (DPDM) has a mass and interacts with electromagnetic fields via kinetic mixing with a coupling constant of $\chi$. Thus, DPDMs are converted into ordinary photons at metal surfaces. Using a millimeter-wave receiver set in a radioshielding box, we performed experiments to detect the conversion photons from the DPDM in the frequency range 10–18 GHz, which corresponds to a mass range 41–74 $\mu \mathrm{e}\mathrm{V}$. We found no conversion photon signal in this range and set the upper limits to $\chi <(0.5\text{–}3.9)\times {10}^{-10}$ at a 95% confidence level.