Dark Matter Results from First 98.7 Days of Data from the PandaX-II Experiment

We report the weakly interacting massive particle (WIMP) dark matter search results using the first physics-run data of the PandaX-II 500 kg liquid xenon dual-phase time-projection chamber, operating at the China JinPing underground laboratory. No dark matter candidate is identified above background. In combination with the data set during the commissioning run, with a total exposure of 3.3×10⁴ kg day, the most stringent limit to the spin-independent interaction between the ordinary and WIMP dark matter is set for a range of dark matter mass between 5 and 1000 GeV/c². The best upper limit on the scattering cross section is found 2.5×10⁻⁴⁶ cm² for the WIMP mass 40 GeV/c² at 90% confidence level.