Low-Mass Dark Matter Search with the DarkSide-50 Experiment.

Area of Science:

• Particle Physics
• Astrophysics
• Cosmology

Background:

• The nature of dark matter remains one of the most significant unsolved problems in physics.
• Weakly Interacting Massive Particles (WIMPs) are a leading candidate for dark matter particles.
• Direct detection experiments aim to observe WIMP interactions with terrestrial detectors.

Purpose of the Study:

• To search for low-mass dark matter WIMPs below 20 GeV/c².
• To establish exclusion limits for WIMP-nucleon cross-sections in an unexplored mass range.
• To improve upon existing dark matter exclusion limits.

Main Methods:

• Utilized the DarkSide-50 detector with a low-radioactivity argon target.
• Collected data over a 6786.0 kg·d exposure.
• Analyzed the ionization signal, with the detector being fully efficient at 0.1 keVee.

Main Results:

• Observed a background rate of approximately 1.5 event/keVee/kg/d at 0.5 keVee, consistent with known sources.
• Achieved a 90% confidence level (C.L.) exclusion limit for spin-independent WIMP-nucleon cross-sections above 1.8 GeV/c².
• Extended dark matter exclusion limits below previous findings in the 1.8-6 GeV/c² mass range.

Conclusions:

• The experiment successfully constrained the parameter space for low-mass WIMP dark matter.
• The results demonstrate the sensitivity of argon-based detectors for WIMP searches.
• Further investigations with larger exposures and improved background rejection are warranted.