Abstract：I will be talking about Dark Matter (DM) direct detection.

DM is one of the most critical questions to be understood and answered in fundamental physics. Among other DM candidates, Weakly Interactive Massive Particles (WIMPs) is the most discussed one. WIMPs direct detection is a research of multi-disciplines which wraps astrophysics, particle physics and nuclear physics together and able to explore the un-touched region of the interaction between WIMPs and nucleon in a way other methods like indirect detection and the searches on colliders can't reach.

I will firstly review the search of DM: the evidence of its existence, the strategy of detection, the current results from various experiments etc. Secondly, two DM direct experiments will be addressed in details: DArk Matter In CCDs (DAMIC) and LUX-ZEPLIN (LZ) which hunt for low-mass (~ 1 - 10 GeV/c^2) and high-mass (~ 10 - 1000 GeV/c^2) WIMPs, respectively. For DAMIC, I will be talking about the quenching factor calibration for a silicon detector and the understanding for the interaction between WIMPs and nucleon under the context of Effective Field Theory (EFT). LZ is the most Spin Independent (SI) sensitive high mass WIMPs searching detector on the stage of construction and has been fully funded by the Department of Energy (DOE), USA. I will introduce the project a little bit, the progress of the assembly of PMT arrays at Brown and the Geant simulation for a calibration of Liquid Xenon (LXe) with 300 keV neutrons.

The last section of my talk would be the introduction of a preliminary proposal hunting for low-mass ~ 100s MeV/c^2 - 10 GeV/c^2 WIMPs: A Liquid HElium dual phase TPC (ALHET). Thanks to the application of two combined experimental techniques: Pulse Shape Discrimination (PSD) and "S2 / S1", ALHET could perform a WIMPs search with the feature of backgrounds free. With ~ 100 kg* yr exposure, ALHEST would be sensitive to the cross section of WIMPs-nucleon at 10^-45 cm^2 for ~ 100s MeV/c^2 - 10 GeV/c^2 WIMPs, which is ~ 5 orders lower than current limits (Dec 2018) and capable of touching the neutrino floor. ALHEST can also be scaled up to ton or multi-tonnes.