Follow-up search for a tentative dark photon signal near $19.5\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{eV}$ using the ORGAN-Q infrastructure

A recent independent dark photon (DP) focused reanalysis of existing data from the TASEH axion haloscope experiment reported a tentative DP dark matter signal with local significance $\ensuremath{\sim}4.7\ensuremath{\sigma}$ at a frequency $f\ensuremath{\approx}4.71\text{ }\text{ }\mathrm{GHz}$, corresponding to ${m}_{X}\ensuremath{\approx}19.5\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{eV}$ and kinetic mixing $ϵ\ensuremath{\sim}6.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$. Motivated by this report, we performed a dedicated, narrowband follow-up experiment to confirm or refute the signal with a cryogenic microwave cavity operated without a magnetic field, leveraging the ORGAN-Q dilution refrigeration and receiver chain. Scanning a window centered on the reported frequency over a live time of ${T}_{\mathrm{int}}\ensuremath{\sim}13\text{ }\text{ }\mathrm{days}$, we find no excess consistent with a dark photon signal as reported, and set a 95% CL of $ϵ\ensuremath{\le}5.04\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ in a narrow mass range around $\ensuremath{\sim}19.5\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{eV}$, excluding a signal of the strength and frequency reported to 99.92% confidence. We discuss the experiment and present the exclusion limits.

journals.aps.org · Physical Review D