Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB

We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based on a method that exploits the extremely low levels of leakage current of the DAMIC detector at SNOLAB of $2–6\times {{10}^{-22}\mathrm{A}\mathrm{cm}}^{-2}$. We evaluate the charge distribution of pixels that collect $<10e^{-}$ for contributions beyond the leakage current that may be attributed to dark matter interactions. Constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and $100\mathrm{MeV}{c}^{-2}$. We also present new constraints on hidden-photon dark matter with masses in the range $1.2–30\mathrm{eV}{c}^{-2}$.

Figure 1

Mean pixel ADU values, after the processing described in the text, as a function of row in the CCD. The first 42 rows correspond to the active region of the CCD, while rows $\ge 43$ correspond to the $y$ overscan. The offset observed in rows $\le 42$ is due to charge accumulated in the pixels.

Figure 2

Distribution of pixel values (with aforementioned conversion constants $\mathrm{\Omega }\approx 14.5\mathrm{ADU}/e^{-}$) for the four CCDs selected for this analysis. An example of best fit result for the leakage-only model (no $\mathrm{DM}\text{−}{e}^{-}$) is given for CCD No. 1 (blue line); the dashed red line is the expectation for a $\mathrm{DM}\text{−}{e}^{-}$ model with $\overline{{\sigma }_e}=1\times {10}^{-33}{\mathrm{cm}}^2$, $m_{\chi }=10\mathrm{MeV}{c}^{-2}$, and $F_{\mathrm{DM}}=1$.

Figure 3

90% C.L upper limits on the DM-electron free scattering cross section $\overline{{\sigma }_e}$ as a function of DM mass $m_{\chi }$ for $F_{\mathrm{DM}}\propto q^{-n}$ ($n=0$, 1, 2) obtained by DAMIC at SNOLAB (solid line). Current best limits from protoSENSEI at MINOS (dotted line) [18, 19], CDMS-HVeV surface run (dashed line) [20], and an analysis of the XENON10 data (dashed-dotted line) [21] are also shown for comparison.

Figure 4

90% C.L. constraints upper limits on the hidden-photon DM kinetic mixing parameter $\kappa$ as a function of the hidden-photon mass $m_V$. Current best direct-detection limits from protoSENSEI at MINOS [18], an analysis of the XENON10 data [24], a dish antenna [25], and astrophysical solar limits [24, 26] are also shown for comparison.