The experiment could help physicists identify signs of WIMP

Jan 18, 2014 19:01 GMT  ·  By
Augusto Brigatti of the Italian Institute for Nuclear Physics stands in the spherical middle chamber of DarkSide-50
   Augusto Brigatti of the Italian Institute for Nuclear Physics stands in the spherical middle chamber of DarkSide-50

An international team of physicists led by experts at the Princeton University last fall turned on a new dark matter detector in southern Italy, at the Gran Sasso National Laboratory (GSNL). The instrument, called DarkSide-50, focuses on searching for weakly-interacting massive particles (WIMP).

These particles are believed to be the main constituents of dark matter, a form of matter that accounts for around 23 percent of the Universe's mass-energy budget. Roughly 4 percent of the same budget is accounted for by baryonic (normal) matter, while dark energy makes up the other 73 percent.

There are numerous candidates for dark matter particles, but many physicists – the GSNL team included – believe that WIMP are among the most promising. This is why DarkSide-50 has been customized according to theories on how these particles should be detected and studied.

The main issue with finding dark matter is that the stuff does not readily interact with baryonic matter, except through gravitational pulls. If they exist, WIMP would not appear on detectors except in the rarest of circumstances.

“This is like the search for the Higgs boson was 10 years ago. We have a good idea of what to look for, but we don't know exactly where or when we will find it,” explains Princeton physics professor and lead scientist for the detector, Peter Meyers.

DarkSide-50 is the result of international collaboration between 17 organizations in the United States, the Italian Institute for Nuclear Physics, and universities in Poland, Ukraine, Russia, China and France.

The detector was assembled inside three caverns at the GSNL, which is itself located under a mountain some 130 kilometers (80 miles) away from Rome. The experiment consists of three fluid-filled chambers, all nestled inside each other.

“Finding dark matter particles would help confirm our understanding of the Universe. And, whether or not we find it, we will have learned a great deal about how to go about looking for it. This is as exciting a moment in the search for dark matter as there has ever been,” says Princeton associate profess of physics Cristiano Galbiati.

One of the main challenges facing the team in its quest to detect elusive dark matter particles is figuring out how to separate possible WIMP signals from the background noise of the experiment. In addition to dark matter, other type of elementary and exotic particles will flow through the chambers as well.

“DarkSide is an attempt to build an apparatus that is as close as possible to an ideal 'background-free detector.' The design benefits from methods and two decades of experience that the Princeton group had developing the Borexino solar neutrino experiment,” concludes Frank Calaprice, who is a professor of physics at Princeton, and the co-leader of the DarkSide-50 experiment with Meyers and Galbiati.