First Results from a Broadband Search for Dark Photon Dark Matter in the $44$ to $52\mu$eV range with a coaxial dish antenna

We present first results from a dark photon dark matter search in the mass range from 44 to 52 $\mu \mathrm{e}\mathrm{V}$ ($10.7-12.5\mathrm{G}\mathrm{H}\mathrm{z}$) using a room-temperature dish antenna setup called GigaBREAD. Dark photon dark matter converts to ordinary photons on a cylindrical metallic emission surface with area $0.5{\mathrm{m}}^2$ and is focused by a novel parabolic reflector onto a horn antenna. Signals are read out with a low-noise receiver system. A first data taking run with 24 days of data does not show evidence for dark photon dark matter in this mass range, excluding dark photon - photon mixing parameters $\chi \gtrsim {10}^{-12}$ in this range at 90% confidence level. This surpasses existing constraints by about two orders of magnitude and is the most stringent bound on dark photons in this range below 49 $\mu$eV.