WIMP Sounds May Provide Clues for Dark Matter Search

A major step in the actual discovery of dark matter, or at least a honing of the discovery process, was performed by the PICASSO project taking place at SNOLAB, in Canada. Scientists came upon a method to refine the search by finding that, under certain conditions, dark matter's WIMPs yield different acoustic signals in terms of amplitude than the alpha particles that render the search process so difficult.

It is known that signals induced by neutrons and dark matter are almost identical, but a new sort of detector based on acoustical signals may enhance the background suppression in the process of dark matter search. Alpha particles, the ones which make the process so difficult, are pretty common on our planet, and are the result of the radioactive nuclei's (thorium or uranium) emissions, so they are also found in the material of the detector. On the other hand, weakly interacting massive particles (WIMPs) are the part of dark matter that interacts very faintly with normal matter and via gravity and the weak nuclear force or a similar force of similar strength. The hypothetical WIMPs are believed to agglomerate in large clouds in the space which separates galaxies. The search for these faint particles is comparable with the one for alien intelligence, since worldwide researchers expect that a WIMP would eventually collide with an atom from their underground detectors.

But the findings of the SNOLAB-based team comprised of Canadian, Czech and American scientists working on the Project In CAnada to Search for Supersymmetric Objects (PICASSO) may yet overcome these difficulties and change the way this research is being done. Their tests on hypersensitive Fluorine superheated liquids, as well as their accurate analyses of the acoustic signals which occur after the phase transitions induced by alpha particles and WIMP-like, neutron-induced recoil nuclei eventually paid off. They were surprised to find out for the first time that there was a distinct acoustic signal amplitude difference.

Viktor Zacek from the University of Montreal explains, “When we looked at our calibration data taken with neutrons and compared them with our alpha background data we saw a peculiar difference which we attributed first to some detector instabilities or gain drifts in our electronics. However when we checked the data and refined the analysis the discrimination effect became even more pronounced”. It remains to be seen how the new discovery will be embraced by the scientific world and whether it will indeed yield better results in the search for the elusive dark matter that accounts for almost a quarter of the universe's matter.