Final Results of the PICASSO Dark Matter Search Experiment

TL;DR

The PICASSO experiment used superheated droplet detectors to search for dark matter, setting new limits on WIMP interactions, but did not observe any dark matter signals, guiding future detector development.

Contribution

This paper presents the final results of the PICASSO dark matter search, including complete data analysis and improved techniques like acoustic localization.

Findings

No dark matter signal was observed.

Set new limits on spin-dependent WIMP-proton interactions.

Excluded certain cross sections for WIMPs around 7 GeV/c².

Abstract

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.