A new result on searching of light dark matter (DM) with PandaX-II experimental data was published online in Physical Review Letters on May 28, 2021 with a title of "Search for Light Dark Matter–Electron Scattering in the PandaX-II Experiment "[1]. This is the 6th PRL paper published with PandaX-II data.
In the last few decades, constraints on DM-nucleon scattering cross section with DM mass above $\rm{GeV/c^{2}}$ become stricter and stricter in the DM direct search experiments. However, sensitivity on DM and free electron scattering is still low because recoil energy is too low to detect. Recently, more theories state light DM could scatters with shell electrons with initial momentum to produce observable signals with recoil energy at keV level. PandaX-II adopted this atomic effect and analyzed ionization-only signals to reduce the analysis energy threshold to 80 eV to search light DM with mass between $\rm{keV/c^{2}}$ and $\rm{GeV/c^{2}}$ for the first time. PandaX-II liquid xenon detector effectively searches for 1821 candidates with a total 46.9 tonne$\cdot$day exposure. We provide the world's most stringent limit within the dark matter mass range from 15 to 30 $\rm{MeV/c^2}$, with the corresponding cross section from $2.5\times10^{-37}$ to $3.1\times10^{-38}$ cm$^2$
