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Could dark matter turn out to be WIMPS?

A Clash of Clusters Provides New Clue to Dark Matter
clash of clusters separates dark from ordinary matter/NASACredit: NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University)

In “New Data Still Have Scientists in Dark Over Dark Matter,” (ScienceDaily, June 8, 2011), we learn:

The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).”We cannot call this a WIMP signal. It’s just what you might expect from it,” said Juan Collar, associate professor in physics at the University of Chicago. Collar and John Orrell of Pacific Northwest National Laboratory, who lead the CoGeNT collaboration, are submitting their results in two papers to Physical Review Letters.

The researchers have not ruled out random fluctuation.

Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science. Although dark matter is invisible to telescopes, astronomers know it is there from the gravitational influence it exerts over galaxies.Job’s not easy:

The putative mass of the WIMP particles that CoGeNT possibly has detected ranges from six to 10 billion electron volts, or approximately seven times the mass of a proton. “To look for WIMPs 10 times heavier is hard enough. If they’re this light, it becomes a nightmare,” Collar said.

What they are seeing is a annual modulation in the already weak signal. Say you get one count a day, then an annual modulation might have an extra 10 counts in December over what you might have expected. This effect, however, could be due to any number of annual effects: a) radioactive snow b) gamma rays from the sun c) more visitors bringing bananas The point being that it is awfully hard to exclude everything until you have a signal in a multi-year data set that is repeatable. Since the Soudan mine had a major fire, and all data collection ceased after 15 months, it is a bit hard to do anything repeatable, but of course, one wants to keep the research money flowing--hence the press release.Robert Sheldon
June 10, 2011
11:05 AM

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