Direct Detection Constraints on Dark Photons with the CDEX-10 Experiment at the China Jinping Underground Laboratory

Abstract

We report constraints on the dark photon effective kinetic mixing parameter ($\ensuremath{\kappa}$) with data taken from two $p$-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on $\ensuremath{\kappa}$ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (${m}_{V}$) from 10 to $300\text{ }\text{ }\mathrm{eV}/{c}^{2}$ in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with ${m}_{V}$ from 0.1 to $4.0\text{ }\text{ }\mathrm{keV}/{c}^{2}$ are set from 449.6 kg-day data, with a minimum of $\ensuremath{\kappa}=1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ at ${\mathrm{m}}_{\mathrm{V}}=200\text{ }\text{ }\mathrm{eV}/{\mathrm{c}}^{2}$.