Search for Dark-Matter-Nucleon Interactions with a Dark Mediator in PandaX-4T

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• The nature of dark matter remains one of the most significant unsolved problems in physics.
• Direct detection experiments aim to observe the faint signals produced by dark matter particles interacting with ordinary matter.
• Previous searches have primarily focused on standard WIMP interactions, leaving open the possibility of interactions via different mediators or with lower mass dark matter candidates.

Purpose of the Study:

• To search for dark-matter-nucleon interactions mediated by a dark sector mediator.
• To set new, stringent limits on the dark matter-nucleon cross-section for low-mass dark matter candidates.
• To probe a specific thermal relic dark matter model involving dark photons and scalar dark matter.

Main Methods:

• Utilized optimized low-energy data from the PandaX-4T liquid xenon experiment.
• Focused on ionization signals only, enhancing sensitivity to low-energy recoils.
• Employed the Migdal effect, which allows for the detection of nuclear recoils that produce detectable ionization signals, extending sensitivity to lower dark matter masses.

Main Results:

• Established the most stringent limits to date on the dark matter-nucleon cross-section for dark matter particle masses in the range of 30 MeV/c² to 2 GeV/c².
• The limits were derived using ionization-only data and the Migdal effect.
• Ruled out significant parameter space for a thermal relic dark matter model where a dark photon decays into scalar dark matter pairs.

Conclusions:

• The PandaX-4T experiment has provided unprecedented sensitivity to low-mass dark matter candidates interacting via a dark mediator.
• The results significantly constrain models of dark matter that involve dark photons and scalar dark matter.
• This study demonstrates the power of using the Migdal effect in direct detection experiments to probe new frontiers in dark matter searches.