First limits on WIMP dark matter from the XENON10 experiment

Abstract

. XENON10 is a dual phase liquid/gas xenon Time Projection Chamber (TPC) for the direct search of Weakly Interacting Massive Particle (WIMP) Dark Matter (DM). The detector, located in the Gran Sasso National Laboratory in Italy, aims at measuring the recoil energy from elastic WIMP-nucleus scattering. It distinguishes electronic interactions (gamma and beta backgrounds) from nuclear recoils based on a different ratio in yields of ionization charge and scintillation light. This discrimination technique reduces background by a factor of 200 – 1000 in the energy range of interest, at a nuclear recoil acceptance of 50%. Background is further reduced by the self-shielding properties of liquid xenon, as the 3D position resolution of the TPC is used to define an inner fiducial volume of low background. XENON10 was extensively calibrated with gamma and neutron sources. A blind search, with data cuts fixed a priori based on calibration data and 16 days of unblinded background data, had an exposure of 136 kg days at a fiducial mass of 5.4 kg. We report our first upper limit on WIMP DM interactions of 8.8 × 10-44 cm2 for a WIMP mass of 100 GeV/c2, which is a factor of 2.3 below the best previous limit.