Search

The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.0 kg of C$_{4}$F$_{10}$ and collected an exposure of 231.4 kgd at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including \mbox{acoustic} localization to allow fiducialization and removal of higher activity regions within the detectors. No signal consistent with dark matter was observed. We set limits for spin-dependent interactions on protons of $\sigma_p^{SD}$~=~1.32~$\times$~10$^{-2}$~pb (90\%~C.L.) at a WIMP mass of 20 GeV/c$^{2}$. In the spin-independent sector we exclude cross sections larger than $\sigma_p^{SI}$~=~4.86~$\times$~10$^{-5 }$~pb~(90\% C.L.) in the region around 7 GeV/c$^{2}$. The pioneering efforts of the PICASSO experiment have paved the way forward for a next generation detector incorporating much of this technology and experience into larger mass bubble chambers., Comment: 24 pages, 7 figures

The Project In CAnada to Search for Supersymmetric Objects (PICASSO) at SNOLAB searches for Weakly Interacting Massive Particle (WIMP) interactions with 19 F. It is particularly sensitive to spin-dependent particle interactions. It uses a droplet technique, based on the principle of a bubble chamber, in which phase transitions in superheated liquids can be triggered by WIMP induced nuclear recoils. The detection process allows a highly e ffi cient suppression of backgrounds from cosmic muons, γ rays and electrons. Recent results and progress are presented and future plans to scale this technique to large masses with the PICO collaboration are briefly discussed.