Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB (1907.12628v2)

Abstract: 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}$ A cm$^{-2}$. We evaluate the charge distribution of pixels that collect $<10~\rm{e^-}$ 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 MeV$c^{-2}$. We also present new constraints on hidden-photon dark matter with masses in the range $1.2$-$30$ eV$c^{-2}$.

Constraints on Light Dark Matter Interactions with Electrons

The paper "Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB" presents significant advancements in the field of dark matter (DM) research, specifically focusing on the detection of light DM particles interacting with electrons. Utilizing the capabilities of the DAMIC (Dark Matter in CCDs) experiment housed at SNOLAB, this research explores parameter spaces for DM electron interactions that were previously unexplored and provides new constraints on hidden-photon DM.

Experimental Methodology and Analysis

The DAMIC experiment operates with advanced Charge-Coupled Devices (CCDs), which are notable for their extremely low leakage current, measured at approximately $4 \, \mathrm{e^- mm^{-2} \, d^{-1}}$ or equivalently $2\textendash6 \, \mathrm{A \, cm^{-2}}$. This characteristic allows the experiment to detect ionization events within the silicon substrate, offering sensitivity to DM interactions that produce minimal energy deposits observable as electronic signals of less than ten charges. The experimental framework employed leverages this sensitivity to investigate light DM particles with masses in the range of 0.6 to 100 MeV/c².

Through a detailed examination of pixel charge distributions, the researchers aim to identify excess charges beyond those predicted by leakage current alone, which could indicate interactions from DM particles. Data were obtained through a series of 100 kilosecond-long exposures, subsequently analyzed for contributions of DM interactions.

Key Results

The paper presents constraints on the interaction cross-section of DM particles with electrons, derived from the sensitive measurements facilitated by the CCD's charge resolution and low noise levels. Importantly, this research explores interactions modeled within a hidden-sector DM scenario, which includes DM coupling via hidden-photon vector bosons. This phenomenology yields sensitivity to a DM mass lower than many conventional approaches, reaching down to approximately 1.2 eV/c².

The DAMIC results place stringent limits on DM-electron cross-sections, surpassing those from existing surface experiments, including protoSENSEI at MINOS and CDMS-HVeV. Additionally, the paper reports improved constraints on the hidden-photon DM parameter space, with kinetic mixing parameters constrained over a mass range from 1.2 to 30 eV/c².

Implications and Future Prospects

These findings contribute substantively to the growing body of direct-detection dark matter research, emphasizing the viability of searching for light dark matter particles. The methodologies and results presented have theoretical implications for hidden-sector models, where DM interacts via photon mixing, thereby enriching the scope of potential DM candidate models.

Looking forward, the paper highlights the potential for enhancing the sensitivity of the DAMIC apparatus. Strategies include reducing the thermal background by cooling the CCDs to 100 K and optimizing the infrastructure ensuring light tightness of the cryostat. Furthermore, a planned expansion to a kilogram-scale detector, DAMIC-M, at the Laboratoire Souterrain de Modane could lead to even more dramatic improvements in detection capability.

This research exemplifies the integration of innovative detection techniques with methodical data analysis to push the boundaries of dark matter discovery, contributing crucial insights into both experimental and astroparticle physics domains.