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 σp = 5.7 × 10 −3 pb at 35 GeV/c 2 in the spin-dependent sector of WIMP-proton interactions, the most restrictive to date for MW ≤ 60 GeV/c 2 from a direct search experiment and overlapping for the first time results previously obtained only indirectly. In the spin-independent sector, a minimum of 4.7 × 10 −6 pb at 35 GeV/c 2 is achieved, with the exclusion contour challenging a significant part of the light mass WIMP region of current interest.The search for weakly interacting massive particle (WIMP) dark matter remains at the forefront of modern physics activity. Estimated to comprise ∼ 23% of the Universe mass, it is the role of direct detection efforts to elaborate its nature, and whether its interaction with nucleons is spin-independent (SI) or spin-dependent (SD). SIMPLE (Superheated Instrument for Massive ParticLe Experiments) [1] is a direct search activity using superheated liquid detectors, and one of only a few in the international panorama with sensitivity to the WIMPproton sector of the SD phase space. It is operated at the 1500 mwe level of the Low Noise Underground Laboratory (LSBB) in southern France.In [1], we reported the first results of a two stage Phase II measurement, comprising a 14.1 kgd Stage 1 exposure of 15 superheated droplet detectors (SDDs) [2-4] with a total active mass of 0.208 kg. We here provide the results of the full Phase II measurement, including a 13.67 kgd Stage 2 exposure of a second 15 SDD set, together with improved neutron shielding and a refined analysis of the individual detector run signals, sensitivities, and nucleation efficiency.A SDD consists of a dispersion of superheated liquid droplets homogeneously distributed within a gel matrix, which may undergo a transition to the gas phase upon energy deposition by incident radiation. Two conditions are required for the nucleation of the gas phase of the superheated droplets [5]: (i) the energy deposited must be greater than a thermodynamic minimum, and (ii) this * criodets@cii.fc.ul.pt energy must be deposited within a thermodynamicallydefined minimum distance (Λr c ) inside the droplet, where Λ is the nucleation parameter and r c = the thermodynamic critical bubble radius. Adjustment of the two conditions results in the necessity of depositions of order ≥ 150 keV/µm for a bubble nucleation, rendering the SDD effectively insensitive to the majority of traditional detector backgrounds (including electrons, γ's and cosmic muons) which complicate more conventional dark matter search detectors, leaving only α-and neutron-induced events.The 15 Stage 2 SDDs were fabricated as described in [1], each containing between 11-19 g of C 2 ...

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Processing the denture base materials produced unequal deformation in different dimensions (anterior-posterior and cross-arch). Each material tested also responded differently to the processing stages.

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