Scientists at Primilab have announced the beginning of a process that will lead to the discovery of dark matter and possibly even super symmetry
With the help of detectors at temperatures very close to absolute zero at a vantage point half a mile underground, physicists from the "Cryogenic Dark Matter Search" announced today (November twelfth, 2003) the beginning of a search that may solve two mysteries that may And it will turn out to be the same: the essence of dark matter, which is found all over the universe, and the question of the existence of super symmetric particles, which are predicted in the theory of particle physics. Scientists at 2 CDMS, an experiment managed by the Energy Department of the Fermi Accelerator Laboratories, hope to discover WIMPs, massive particles whose effect on matter is tiny (Weakly Interacting Massive Particles), the leading candidates for explaining dark matter. These particles may turn out to be neutralinos, yet-to-be-discovered particles whose existence was predicted by the supersymmetry theory.
"It seems that there is an arrow from particle physics and an arrow from cosmology, both pointing in the same direction," said Dan Akrib, deputy director of the 2 CDMS project at Case Western Reserve University. "The discovery of neutralinos would be a huge achievement for cosmology and particle physics."
The 2nd CDMS experiment, the result of the collaboration of scientists from 12 institutions and the support of the Office of Science of the US Department of Energy (DOE - Department of Energy) and the support of the National Science Foundation, uses a detector, which is located deep underground in the historic iron mine in the Northeast Minnesota. The experimenters will look for WIMPs, particles more massive than a proton, but their interaction with matter is so weak that thousands of them will pass through your body in a second without leaving a trace.
Remarkably, in this type of merger that is gaining the attention of physicists, the properties of the missing cosmic matter appear to match those of the supersymmetric neutralinos.
"Either it's a cosmic coincidence, or the universe is trying to tell us something," said Dan Bauer of Permilab, director of the 2CDMS project.
From observing the rotation of galaxies - how gravity affects the stars in the galaxy - astronomers have known for 70 years that the matter we see cannot make up all the matter in the universe. If it was indeed all the matter in the universe, the galaxies would break up. Recent calculations indicate that normal matter consisting of atoms constitutes only 4% of the energy content of the universe. "Dark energy" makes up about 73%, and an unknown form of dark matter makes up about 23%.
"It is often said that this is the ultimate Copernican revolution," said David Caldwell, a physicist at the University of California, Santa Barbara and chairman of the 2nd CDMS Executive Committee. "Not only are we not at the center of the universe, we are not even made of the same material as most of it."
Measurements of the cosmic background radiation, radiation left over from the Big Bang, have recently placed severe constraints on the nature and quantity of dark matter. The lightweight neutrino can only account for a few percent of the missing mass. If a neutrino was the main component of dark matter, it would have left its imprint on the cosmic background radiation, so the Wilkinson Background Nonuniformity Probe would have detected it, but it did not.
At the same time, particle physicists continued to search for particles that would go beyond the Standard Model, the theory of elementary particles and their interactions. Super symmetry, a theory that brings us closer to the unification of the four forces, predicts that every particle of matter has a massive super symmetric partner. No one has yet predicted such a partner particle. The theory describes the neutralino as the lightest and most stable neutral supersymmetric particle, an important property of dark matter. The expected abundance of the neutrino and the rate at which it interacts with other particles also make it a likely candidate for dark matter, and Caldwell noted the effect 2 CDMS might have.
"Discovery of these particles", he said, "will be a huge breakthrough, one of the most important in the century".
A WIMP particle will only rarely hit the Earth's core, and the "background noise" from more routine particle events, such as the cosmic rays that routinely bombard the Earth, will mostly drown out these rare interactions. The location of the detector of the 2 CDMS 740 meters below the surface of the ground masks most of the particle "noise" from cosmic rays. Cooling the detector to a temperature of about 50 thousand degrees above absolute zero reduces the heat energy in the background and enables the detection of individual collisions of particles. Bower from Premilab estimates that if the "background noise" is low enough, CDMS only needs a few individual interactions to give a solid claim on the discovery of WIMPs.
"The powerful technology we use allows for the unequivocal detection of events in crystals caused by any unknown form of matter," said one of the CDMS spokespersons, Bernard Sedolt of the University of California at Berkeley.
Another speaker, Blas Cabrera of Stanford University, agreed with Sedolt's words.
"We believe that we have the best system in the world in terms of being able to detect WIMPs," said Cabrera.
"This effort is a good example of the collaboration between DOE's Office of High Energy Physics and the National Science Foundation in trying to help scientists find the source of dark matter in the universe," said Raymond Auerbach, chief of the US Department of Energy's Office of Science.
"2 CDMS is the kind of innovative and groundbreaking research that the National Science Foundation is proud to support," said Michael Turner, assistant director for mathematical and physical sciences at the National Science Foundation. "If the experiment detects a signal, it may tell us what dark matter is and provide us with an important clue as to how gravity integrates with the other forces. This kind of experiment shows how the universe can be used as a laboratory to obtain answers to some of the most fundamental questions we can ask. It also shows how the Department of Energy and the National Science Foundation work together."
While the 2 CDMS searches for dark matter, scientists at the Tevatron particle accelerator at Paralab will try to create neutralinos by causing collisions between protons and antiprotons.
"CDMS can give us the mass and the rate of interactions of the WIMP," said Roger Dixon of Paramilab. "But an accelerator is needed to tell us if this is the neutralino."
2 CDMS collaborators include Brown University, Case Western Reserve University, Fermi National Accelerator Laboratories, Lawrence Berkeley National Accelerator Laboratories, National Institute of Standards and Technology, Princeton University, Santa Clara University, Stanford University, UC Berkeley, UC Santa Barbara , University of Colorado at Denver and University of Minnesota.
Funding for the CDMS 2 experiment comes from the US Department of Energy's Office of Science and the US National Science Foundation's Energy and Astronomy Division.
Permilab is a national laboratory, funded by the Office of Science of the US Department of Energy and operated by the University Research Association.
Link to the original message on Permilab's website
Link to information about the 2nd CDMS trial
From a press release on behalf of Paramilab. Translation: Dikla Oren
