Final Analysis and Results of the Phase II SIMPLE Dark Matter Search

TL;DR

This paper presents the final results of the Phase II SIMPLE dark matter search, setting new leading limits on WIMP-proton spin-dependent interactions and challenging recent claims in the spin-independent sector.

Contribution

It provides the most restrictive direct search limits to date on WIMP-proton spin-dependent interactions and refines analysis techniques for superheated droplet detectors.

Findings

Set a minimum cross-section of 4.2 x 10^-3 pb at 35 GeV/c^2 for spin-dependent interactions.

Achieved a minimum of 3.6 x 10^-6 pb at 35 GeV/c^2 for spin-independent interactions.

Challenged the recent CoGeNT region with new exclusion limits.

Abstract

We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, the second stage including an improved neutron shielding. The analyses includes a refined signal analysis, and revised nucleation efficiency based on reanalysis of previously-reported monochromatic neutron irradiations. The combined results yield a contour minimum of \sigma_{p} = 4.2 x 10^-3 pb at 35 GeV/c^2 on the spin-dependent sector of WIMP-proton interactions, the most restrictive to date from a direct search experiment and overlapping for the first time results previously obtained only indirectly. In the spin-independent sector, a minimum of 3.6 x 10^-6 pb at 35 GeV/c^2 is achieved, with the exclusion contour challenging the recent CoGeNT region of current interest.