Shedding Light on Mirror Dark Matter Using CDEX

Abstract

Mirror dark matter, a hidden-sector counterpart to the Standard Model with identical particle content, could be detectable through photon-mirror-photon kinetic mixing $(\epsilon)$. We present new constraints from CDEX-10 low-energy recoil data, establishing $\epsilon < 2 \times 10^{-10}$ for mirror nuclear dark matter in the 10--56 GeV mass range. Projections for CDEX-300 (with 95 days of exposure) show significantly improved sensitivity, reaching $\epsilon < 3.75 \times 10^{-11}$ for a local mirror halo temperature below 0.3 keV, surpassing existing constraints from LUX and positronium decays. These results demonstrate CDEX-300's unique capability to probe kinetic-mixing parameter space, providing stringent constraints on mirror dark matter models.