The Picasso Experiment


As of July 2009 PICASSO reports new results for spin-dependent WIMP interactions on 19F!

No dark matter signal has been found, but for WIMP masses of 24 Gev/c2 new stringent limits have been obtained on the spin-dependent cross section for WIMP scattering on 19F of 13.9 pb (90% CL). This result has been converted into a cross section limit for WIMP interactions on protons of 0.16 pb (90% CL). The obtained limits restrict recent interpretations of the DAMA/LIBRA annual modulation effect in terms of spin dependent interactions.

When the results of an experiment produce new "limits" as PICASSO now has, it means that the experiment was able to do increase its sensitivity, but is still not sensitive enough to detect dark matter-matter interactions. Because many aspects of dark matter are not well-understood, we are not sure how much sensitivity will be needed to detect it. Therefore experiments are constantly improving their sensitivity and at some point conclusive evidence (probably from more than one experiment) for dark matter should be obtained. Since the sensitivity of the PICASSO experiment increases with the number of detectors and the length of time they are operated, new levels of sensitivity will soon be achieved from all 32 detectors now installed and running.

 These latest PICASSO results were released at the eleventh international conference on Topics in Astroparticle and Underground Physics - TAUP2009 and a paper has been published in Phys. Lett. B (682) 2009, 185.  The paper can be found on the web at 

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