  Experimental efforts of the last decades have been unsuccessful in detecting
WIMPs (Weakly Interacting Massive Particles) in the 10-to-10$^4$ GeV/$c^2$
range, thus motivating the search for lighter dark matter. The DAMIC (DArk
Matter In CCDs) at SNOLAB experiment aims for direct detection of light dark
matter particles ($m_\chi <$ 10 GeV/$c^2$) by means of CCDs (Charge-Coupled
Devices). Fully-depleted 675 $\mu$m-thick CCDs are used to such end. The
optimized readout noise and operation at cryogenic temperatures allow for a
detection threshold of 50 eV$_{\text{ee}}$ electron-equivalent energy. Focusing
on nuclear and electronic scattering as potential detection processes, DAMIC
has so far set competitive constraints on the detection of low mass WIMPs and
hidden-sector particles. In this work, an 11 kg-day exposure dataset is
exploited to search for light WIMPs by building the first comprehensive
radioactive background model for CCDs. Different background sources are
discriminated making conjoint use of the spatial distribution and energy of
ionization events, thereby constraining the amount of contaminants such as
tritium from silicon cosmogenic activation and surface lead-210 from radon
plate-out. Despite a conspicuous, statistically-significant excess of events
below 200 eV$_{\text{ee}}$, this analysis places the strongest exclusion limit
on the WIMP-nucleon scattering cross section with a silicon target for 1 GeV $<
m_\chi c^2<$ 9 GeV.

Cosmology and Nongalactic Astrophysics;Instrumentation and Detectors