First Science Results from ZEPLIN-III

ZEPLIN-III uses a 12 kg two-phase xenon time projection chamber to search for the weakly interacting massive particles (WIMPs) that may account for the dark matter of our Galaxy. The detector measures both scintillation and ionisation produced interactions in the liquid to differentiate between nuclear recoils expected from WIMPs and electron recoil background signals down to ∼10 keV nuclear recoil energy. Analysis of 847 kg·days of data acquired between February 27th 2008 and May 20th 2008 has excluded a WIMP-nucleon elastic scattering spin-independent cross-section above 8.1x10∼-8 pb at 60 GeVc-2 with a 90% confidence limit. ZEPLIN-III demonstrated better discrimination at low-energy than previously achieved by any other xenon-based experiments.