Directly Detecting MeV-Scale Dark Matter Via Solar Reflection.

Area of Science:

• Particle Physics
• Astrophysics
• Cosmology

Background:

• The nature of dark matter (DM) remains one of the most significant unsolved problems in physics.
• Direct detection experiments search for DM particles interacting with terrestrial detectors.
• The interaction of DM with solar material has been proposed as a potential signal amplification mechanism.

Purpose of the Study:

• To investigate the impact of DM-electron scattering within the solar interior on the detectable DM spectrum.
• To derive new constraints on the DM-electron scattering cross-section (σe) for light DM particles.
• To project the sensitivity of future low-threshold direct detection experiments.

Main Methods:

• Numerical simulation of the reflected DM flux after interaction within the Sun.
• Calculation of the expected signal from DM scattering on detector electrons.
• Analysis of existing data from XENON10/100, LUX, PandaX-II, and XENON1T experiments.

Main Results:

• Light DM particles (MeV/c² range) scattering off electrons in the Sun produce a hardened spectrum detectable on Earth.
• The reflected DM component can be significantly more energetic than the ambient galactic DM.
• New constraints on σe in the MeV and sub-MeV mass ranges were derived.

Conclusions:

• The Sun can act as a "reflector" for light dark matter, enhancing its detectability.
• Existing direct detection experiments provide valuable constraints on light DM properties.
• Future low-threshold experiments hold promise for further probing this dark matter interaction channel.