A direct dark matter search in XMASS-I

Abstract

A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We have used 705.9 live days of data in a fiducial volume containing 97 kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was $(4.2\pm 0.2)\times 10^{-3}\mathrm{da}{\mathrm{y}}^{-1}\mathrm{k}{\mathrm{g}}^{-1}\mathrm{ke}{\mathrm{V}}_{\mathrm{ee}}^{-1}$ at $5\mathrm{ke}{\mathrm{V}}_{\mathrm{ee}}$, with a signal efficiency of $20\%$. All the remaining events are consistent with our background evaluation, mostly of the "mis-reconstructed events" originated from ${}^{210}$Pb in the copper plates lining the detector's inner surface. The obtained upper limit on a spin-independent WIMP-nucleon cross section was $2.2\times 10^{-44}\mathrm{c}{\mathrm{m}}^2$ for a WIMP mass of $60GeV/{\mathrm{c}}^2$ at the $90\%$ confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors.

16 pages, 8 figures