WIMP-nucleon cross-section results from the second science run of ZEPLIN-III

TL;DR

This paper presents upper limits on WIMP-nucleon cross sections from ZEPLIN-III's second science run, improving constraints on dark matter interactions using liquid xenon detectors.

Contribution

First to report results from ZEPLIN-III's second run, significantly tightening WIMP cross-section limits with extended exposure and combined data analysis.

Findings

Excluded scalar cross-section above 4.8E-8 pb at 50 GeV/c^2 WIMP mass

Achieved combined limit of 3.9E-8 pb with first and second run data

Set WIMP-neutron spin-dependent cross-section limit at 8.0E-3 pb

Abstract

We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1,344 kg.days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7-29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8E-8 pb near 50 GeV/c^2 WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9E-8 pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0E-3 pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach.