## PandaX: Particle and Astrophysical Xenon Experiments

PandaX is a staged experimental program that utilizes xenon detectors to search for elusive dark matter particles and understand neutrinos' fundamental properties. The PandaX collaboration has now entered into the multi-ton stage, PandaX-4T.

PandaX-II is a dark matter direct detection experiment equipped with a half-ton scale dual-phase time projection chamber (TPC), operated in CJPL between Oct. 2014 and June 2019. In 2016 and 2017, PandaX-II produced the world leading constraints to dark matter-nucleon interactions. See a list of scientific publications here.

With 6-ton of total Xenon and 4-ton sensitive target, PandaX-4T aims to improve the dark matter sensitivity by one order of magnitude in comparison to PandaX-II. PandaX-4T also plans to make sensitive searches on neutrinoless double beta decay of ${}^{136}Xe$ , and other signals from new physics. This project is expected to commence data taking in 2021.

PandaX-III searches for the possible neutrinoless double beta decay with 200 kg to one ton of 90% enriched ${}^{136}Xe$ in a high pressure gaseous Xenon TPC.

## News

• PandaX-4T is not just a dark matter detector, as you may be more familiar with. For such a large and exquisite detector, we can explore multiple physics topics. Neutrino physics is one such important direction.

• Background neutrinos can elastically scatter with target nucleus (coherently elastic neutrino-nucleus scattering or CEvNS), producing nuclear recoil signals in a dark matter detector that can mimic dark matter signals. This intrinsic background is the so-called “neutrino floor”, which will ultimately limit the sensitivity of dark matter direct detection. On the other hand, it also provides very interesting physics opportunities to study neutrino interactions.

• With the extra energy gained from the cosmic rays, sub-GeV dark matter particles can produce visible recoil signals in the detector. We present a new result searching for the cosmic ray boosted dark matter (CRDM) with the PandaX-II full data. This work is motivated by the theoretical paper (PRL. 126 091804), which first pointed out that a sidereal diurnal modulation in signal rate and energy spectrum due to the Earth shielding is expected for low mass CRDM.

• On December 24, 2021, the first dark matter search result from PandaX-4T, a liquid xenon detection experiment, was published in Physical Review Letters as the "Editor's Suggestion" [1]. The American Physical Society 《Physics》 reported this PandaX-4T latest result together with another result from the Axion Dark Matter Experiment with a title of "Tightening the Net on Two Kinds of Dark Matter"

• 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.