Search for light dark matter with ionization signals in the PandaX-4T Experiment

TL;DR

This paper reports on the search for light dark matter using ionization signals in the PandaX-4T liquid xenon detector, setting new limits on dark matter interactions across a broad mass range.

Contribution

It presents the first results from PandaX-4T using ionization signals to search for light dark matter, establishing the most stringent limits in several mass ranges.

Findings

Set new limits on dark matter-electron interactions from 40 MeV/c^2 to 10 GeV/c^2.

Established the most stringent constraints on dark matter-nucleon interactions in the 3.2 to 4 GeV/c^2 range.

Limits approach parameter space predicted by early Universe dark matter production models.

Abstract

We report the search results of light dark matter through its interactions with shell electrons and nuclei, using the commissioning data from the PandaX-4T liquid xenon detector. Low energy events are selected to have an ionization-only signal between 60 to 200 photoelectrons, corresponding to a mean nuclear recoil energy from 0.77 to 2.54 keV and electronic recoil energy from 0.07 to 0.23 keV. With an effective exposure of 0.55 tonne$\cdot$year, we set the most stringent limits within a mass range from 40 $\rm{MeV/c^2}$ to 10 $\rm{GeV/c^2}$ for point-like dark matter-electron interaction, 100 MeV/c$^2$ to 10 GeV/c$^2$ for dark matter-electron interaction via a light mediator, and 3.2 to 4 $\rm{GeV/c^2}$ for dark matter-nucleon spin-independent interaction. For DM interaction with electrons, our limits are closing in on the parameter space predicted by the freeze-in and freeze-out mechanisms in the early Universe.