Doug M. Boyer

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

We report the final results of the Phase II SIMPLE measurements, comprising two run stages of 15 superheated droplet detectors each, with the second stage including an improved neutron shielding. The analyses include a refined signal analysis, and revised nucleation efficiency based on a reanalysis of previously reported monochromatic neutron irradiations. The combined results yield a contour minimum of σp=5.7×10(-3)  pb at 35  GeV/c2 in the spin-dependent sector of weakly interacting massive particle (WIMP) proton interactions, the most restrictive to date for MW}≤60  GeV/c2 from a direct search experiment and overlapping, for the first time, with results previously obtained only indirectly. In the spin-independent sector, a minimum of 4.7×10(-6)  pb at 35  GeV/c2 is achieved, with the exclusion contour challenging a significant part of the light mass WIMP region of current interest.

SIMPLE dark matter search results

We report an improved SIMPLE experiment comprising four superheated droplet detectors with a total exposure of 0.42 kgd. The result yields similar to factor 10 improvement in the previously-reported results, and-despite the low exposure-is seen to provide restrictions on the allowed phase space of spin-dependent coupling strengths almost equivalent to those from the significantly larger exposure NAIAD-CDMS/ZEPLIN searches. (c) 2005 Elsevier B.V. All rights reserved.

First Results of the Phase II SIMPLE Dark Matter Search

We report results of a 14.1   kg d measurement with 15 superheated droplet detectors of total active mass 0.208 kg, comprising the first stage of a 30 kg d Phase II experiment. In combination with the results of the neutron-spin sensitive XENON10 experiment, these results yield a limit of |a(p)|<0.32 for M(W)=50 GeV/c² on the spin-dependent sector of weakly interacting massive particle-nucleus interactions with a 50% reduction in the previously allowed region of the phase space, formerly defined by XENON, KIMS, and PICASSO. In the spin-independent sector, a limit of 2.3×10⁻⁵ pb at M(W)=45 GeV/c² is obtained.

SIMPLE limits on spin-dependent WIMP interactions

An improved SIMPLE experiment comprising four superheated droplet detectors with a total exposure of 0.42 kg.d yields ~factor 10 improvement in the previously-reported results. Despite the low exposure, the result provides restrictions on the allowed phase space of spin-dependent coupling strengths almost equivalent to those from the significantly larger exposure NAIAD-CDMS/ZEPLIN searches.

Recent results from the SIMPLE dark matter search

We present the results of the recent Phase II SIMPLE search effort, comprising two stages each of ~14 kgd exposure of 15 Superheated Droplet Detectors with ~0.2 kg active mass and recoil energy threshold of 8 keV. In the second stage, the neutron shielding was increased to reduce the on-detector rate by a factor 3.5. Combined with an improved nucleation efficiency and analysis of the detector pressure evolution during the measurements, the results yield improved results in the phase space of both spin -dependent and -independent WIMP interactions.