We report the results of a weakly-interacting massive particle (WIMP) dark matter search using the full 80.1;live-day exposure of the first stage of the PandaX experiment (PandaX-I) located in the China Jin-Ping Underground Laboratory. The PandaX-I d
etector has been optimized for detecting low-mass WIMPs, achieving a photon detection efficiency of 9.6%. With a fiducial liquid xenon target mass of 54.0,kg, no significant excess event were found above the expected background. A profile likelihood analysis confirms our earlier finding that the PandaX-I data disfavor all positive low-mass WIMP signals reported in the literature under standard assumptions. A stringent bound on the low mass WIMP is set at WIMP mass below 10,GeV/c$^2$, demonstrating that liquid xenon detectors can be competitive for low-mass WIMP searches.
We report on the first dark-matter (DM) search results from PandaX-I, a low threshold dual-phase xenon experiment operating at the China Jinping Underground Laboratory. In the 37-kg liquid xenon target with 17.4 live-days of exposure, no DM particle
candidate event was found. This result sets a stringent limit for low-mass DM particles and disfavors the interpretation of previously-reported positive experimental results. The minimum upper limit, $3.7times10^{-44}$,cm$^2$, for the spin-independent isoscalar DM-particle-nucleon scattering cross section is obtained at a DM-particle mass of 49,GeV/c$^2$ at 90% confidence level.
We describe the automated calibration system for the antineutrino detectors in the Daya Bay Neutrino Experiment. This system consists of 24 identical units instrumented on 8 identical 20-ton liquid scintillator detectors. Each unit is a fully automat
ed robotic system capable of deploying an LED and various radioactive sources into the detector along given vertical axes. Selected results from performance studies of the calibration system are reported.
We study the feasibility of a sterile neutrino search at the China Advanced Research Reactor by measuring $bar { u}_e$ survival probability with a baseline of less than 15 m. Both hydrogen and deuteron have been considered as potential targets. The s
ensitivity to sterile-to-regular neutrino mixing is investigated under the 3(active)+1(sterile) framework. We find that the mixing parameter $sin^2(2theta_{14})$ can be severely constrained by such measurement if the mass square difference $Delta m_{14}^2$ is of the order of $sim$1 eV$^2$.
A precise measurement of the neutron decay $beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 a
nd 2009, we report $A_0 = -0.11966 pm 0.00089_{-0.00140}^{+0.00123}$, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon $g_A/g_V = -1.27590_{-0.00445}^{+0.00409}$.
