Evidence for mirror dark matter from the CDMS low energy electron recoil spectrum

We point out that mirror dark matter predicts low-energy ($E_R\lesssim 2\mathrm{keV}$) electron recoils from mirror electron scattering as well as nuclear recoils from mirror ion scattering. The former effect is examined and applied to the recently released low-energy electron recoil data from the CDMS Collaboration. We speculate that the sharp rise in electron recoils seen in CDMS below 2 keV might be due to mirror electron scattering and show that the parameters suggested by the data are roughly consistent with the mirror dark matter explanation of the annual modulation signal observed in the DAMA/Libra and DAMA/NaI experiments. Thus, the CDMS data offer tentative evidence supporting the mirror dark matter explanation of the DAMA experiments, which can be more rigorously checked by future low-energy electron recoil measurements.

Figure 1

Efficiency corrected low-energy electron-scattering spectrum as measured by CDMS/Ge [16]. The dashed line is a simple background model.

Figure 2

Mirror dark matter induced electron $\mathrm{\text{recoils}}+\mathrm{\text{background}}$ model, for the parameters $Y_{H{e}^{\prime }}=0.9$ and $ϵ=6\times {10}^{-10}$ (dashed line), $ϵ=7\times {10}^{-10}$ (solid line), and $ϵ=8\times {10}^{-10}$ (dotted line), compared with the CDMS/Ge data.

Figure 3

Mirror dark matter induced electron $\mathrm{\text{recoils}}+\mathrm{\text{background}}$ model, for fixed $ϵ=7\times {10}^{-10}$ and $Y_{H{e}^{\prime }}=0.3$ (dotted line), $Y_{H{e}^{\prime }}=0.6$ (dashed line), and $Y_{H{e}^{\prime }}=0.9$ (solid line).