W. Y. Tang

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (${m}_{\ensuremath{\chi}}$) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in ${m}_{\ensuremath{\chi}}$ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on ${\ensuremath{\sigma}}_{\ensuremath{\chi}N}^{\mathrm{SI}}$ at 90% confidence level are derived as $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}32}\ensuremath{\sim}7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}35}\text{ }\text{ }{\mathrm{cm}}^{2}$ for TI analysis at ${m}_{\ensuremath{\chi}}\ensuremath{\sim}50--180\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, and $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}32}\ensuremath{\sim}9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}38}\text{ }\text{ }{\mathrm{cm}}^{2}$ for AM analysis at ${m}_{\ensuremath{\chi}}\ensuremath{\sim}75\text{ }\text{ }\mathrm{MeV}/{c}^{2}--3.0\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}42}$ and $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}36}\text{ }\text{ }{\mathrm{cm}}^{2}$ at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (${m}_{\ensuremath{\chi}}$) of $5\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ are achieved. The lower reach of ${m}_{\ensuremath{\chi}}$ is extended to $2\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

We report constraints on the dark photon effective kinetic mixing parameter ($\ensuremath{\kappa}$) with data taken from two $p$-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90% confidence level upper limits on $\ensuremath{\kappa}$ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (${m}_{V}$) from 10 to $300\text{ }\text{ }\mathrm{eV}/{c}^{2}$ in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90% confidence level with ${m}_{V}$ from 0.1 to $4.0\text{ }\text{ }\mathrm{keV}/{c}^{2}$ are set from 449.6 kg-day data, with a minimum of $\ensuremath{\kappa}=1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ at ${\mathrm{m}}_{\mathrm{V}}=200\text{ }\text{ }\mathrm{eV}/{\mathrm{c}}^{2}$.

We present improved germanium-based constraints on sub-GeV dark matter via dark matter--electron ($\ensuremath{\chi}\text{\ensuremath{-}}e$) scattering using the $205.4\text{ }\text{ }\mathrm{kg}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{day}$ dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted $\ensuremath{\chi}\text{\ensuremath{-}}e$ scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for ${m}_{\ensuremath{\chi}}$ larger than $80\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ compared to previous germanium-based $\ensuremath{\chi}\text{\ensuremath{-}}e$ results. We also present the most stringent $\ensuremath{\chi}\text{\ensuremath{-}}e$ cross-section limit to date among experiments using solid-state detectors for ${m}_{\ensuremath{\chi}}$ larger than $90\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ with heavy mediators and ${m}_{\ensuremath{\chi}}$ larger than $100\text{ }\text{ }\mathrm{MeV}/{\mathrm{c}}^{2}$ with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new $\ensuremath{\chi}\text{\ensuremath{-}}e$ detection method with high-purity germanium detectors in ultralow radioactive background.

Dark matter direct detection experiments mostly operate at deep underground laboratories. It is necessary to consider shielding effect of the Earth, especially for dark matter particles interacting with a large cross section. We analyzed and simulated the Earth shielding effect for dark matter at the China Jinping Underground Laboratory (CJPL) with a simulation package, CJPL Earth Shielding Simulation code (CJPL_ESS), which is applicable to other underground locations. The further constraints on the $\ensuremath{\chi}\text{\ensuremath{-}}\mathrm{N}$ cross section exclusion regions are derived based on the studies with CDEX experiment data.