Final Results of the PICASSO Dark Matter Search Experiment

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 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 σ p S D  = 1.32 ×  10 −2 − 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 σ p S I  = 4.86 ×  10 −5 − 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.