Search for Light Dark Matter with Ionization Signals in the PandaX-4T Experiment.

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• Dark matter remains one of the most significant mysteries in modern physics.
• Understanding dark matter's nature requires direct detection experiments probing various interaction models.
• Light dark matter candidates are particularly challenging to detect due to their weak interactions.

Purpose of the Study:

• To search for light dark matter particles through their interactions with electrons and nuclei.
• To set new experimental limits on dark matter properties using commissioning data from the PandaX-4T detector.
• To constrain theoretical models of dark matter, including freeze-in and freeze-out mechanisms.

Main Methods:

• Utilized commissioning data from the PandaX-4T liquid xenon detector.
• Selected low-energy events with ionization-only signals (60-200 photoelectrons).
• Analyzed data with an effective exposure of 0.55 tonne-year to set limits.

Main Results:

• Established the most stringent limits for pointlike dark matter-electron interactions (40 MeV/c² to 10 GeV/c²).
• Set new limits for dark matter-electron interactions via a light mediator (100 MeV/c² to 10 GeV/c²).
• Constrained dark matter-nucleon spin-independent interactions (3.2 to 4 GeV/c²).

Conclusions:

• The results significantly narrow down the parameter space for light dark matter.
• Experimental limits approach predictions from early Universe dark matter production mechanisms.
• PandaX-4T demonstrates powerful capabilities for probing light dark matter candidates.