Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX Data

We present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including 1.4 x 10(4) kg day of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium beta source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signal only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4 GeV c(-2), these new results give the most stringent direct limits on the spin- independent WIMP- nucleon cross section. The 90% C. L. upper limit has a minimum of 0.6 zb at 33 GeV c(-2) WIMP mass.