T. Morlat

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.

Discrimination of nuclear recoils from alpha particles with superheated liquids

The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron-induced recoils.

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.

Fabrication and response of high concentration SIMPLE superheated droplet detectors with different liquids

Abstract The combined measurement of dark matter interactions with different superheated liquids has recently been suggested as a cross-correlation technique in identifying WIMP candidates. We describe the fabrication of high concentration superheated droplet detectors based on the light nuclei liquids C3F8, C4F8, C4F10 and CCl2F2, and investigation of their irradiation response with respect to C2ClF5. The results are discussed in terms of the basic physics of superheated liquid response to particle interactions, as well as the necessary detector qualifications for application in dark matter search investigations. The possibility of heavier nuclei SDDs is explored using the light nuclei results as a basis, with CF3I provided as an example.

New limits on WIMP interactions from the SIMPLE dark matter search

The SIMPLE project uses superheated C2ClF5 liquid detectors to search for particle dark matter candidates. We report the results of the first stage exposure (14.1 kgd) of its latest two-stage, Phase II run, with 15 superheated droplet detectors of total active mass 0.208 kg. In combination with the results of the neutron-spin sensitive XENON10 experiment, these results yield a limit of |ap| < 0.32, |an| < 0.17 for MW = 50 GeV/c 2 on the model-independent, spin-dependent sector of weakly interacting massive particle (WIMP)-nucleus interactions, and together yield a 50% reduction in the previously allowed region of the phase space. The result provides a contour minimum of σp ~ 2.8 x 10 -2 pb at MW = 45 GeV/c 2 , constituting the most restrictive direct detection limit to date against a spin-dependent WIMP-proton coupling. In the spin-independent sector, the result is seen to offer the prospect of contributing to the question of light mass WIMPs with an improvement in the current understanding of its nucleation efficiency.

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.

Heavy Superheated Droplet Detectors as a Probe of Spin-independent WIMP Dark Matter Existence

At present, application of Superheated Droplet Detectors (SDDs) in WIMP dark matter searches has been limited to the spin-dependent sector, owing to the general use of fluorinated refrigerants which have high spin sensitivity. Given their recent demonstration of a significant constraint capability with relatively small exposures and the relative economy of the technique, we consider the potential impact of heavy versions of such devices on the spin-independent sector. Limits obtainable from a

Signal Discrimination in Superheated Droplet Detectors

{\mathrm{CF}}_{3}\mathrm{I}

WIMP SEARCHES WITH SUPERHEATED DROPLET DETECTORS: STATUS AND PROSPECTS

-loaded SDD are estimated on the basis of the radiopurity levels and backgrounds already achieved by the SIMPLE and PICASSO experiments. With 34 kgd exposure, equivalent to the current CDMS, such a device may already probe to below