AbstractsAstronomy & Space Science

The final results of the PICASSO experiment, with 409 kg days of exposure collected from November 2012 to January 2014, have yielded new limits for Spin-Dependent and Spin-Independent Dark Matter interactions.\\ The data collected and the various backgrounds were assiduously studied using Monte Carlo simulations and a new set of sophisticated analysis techniques including the wavelet analysis presented in this thesis. In general, a good suppression of most backgrounds was attained. The neutron background event rate was reduced to about a factor of 10 compared to the previous phase of the experiment. Electronic and acoustic noise events were thoroughly suppressed. A new class of ``mystery events'' were removed as well. All that remained was the irreducible alpha background.\\ No signal consistent with a WIMP Dark Matter hypothesis was observed. Consequently, an exclusion curve was obtained with a minimum limit at ${90\%}$ C.L. of ${\sigma_{\chi p}^{SD} =0.0228}$ pb at a WIMP mass of 20 GeV/$c^2$ in the Spin-Dependent sector. By combining results from 2012 and the current results, an improved constraint of ${\sigma_{\chi p}^{SD}}$(90${\%}$ C.L.) ${=0.0188}$ pb at 20 GeV/$c^2$ was placed on the Dark Matter interaction with protons in the Fluorine nuclei used in the detectors.\\ In addition, the new limits on WIMP-proton interactions in the Spin Independent sector exclude the DAMA/LIBRA results (at ${90\%}$ C.L.) for low masses below 12 GeV/$c^2$ and further constrain the published CRESST and CDMS Si discovery regions at low WIMP masses.