New data still have scientists in dark over dark matter

New data still have scientists in dark over dark matter

www.physorg.com

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....

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"Weakly Interacting Massive Particles" are being sought. And here's the analogy that applies to the effort....

WIMPs would be moving in random directions in this halo, at velocities similar to the sun’s. “You find yourself in a situation similar to a car moving through a cloud of gnats,” Collar explained. “The faster the car goes, the more gnats will hit the front windshield.”

But the Earth's relative speed moving through the 'cloud of gnats' is not constant....

The sun moves in the plane of the galaxy on the outskirts of one of its spiral arms at a speed of 220 kilometers per second (136 miles per second). The Earth orbits the sun at 15 kilometers per second (18.5 miles per second). During winter, Earth moves in roughly the opposite direction of the sun’s movement through the galaxy, but during summer, their motion becomes nearly aligned in the same direction. This alignment increases Earth’s net velocity through a galactic halo of dark matter particles, whose existence scientists have inferred from numerous astronomical observations.

So this could mean that the variations in the decade-old Italian detector experiment may not be so questionable after all.

Collar and his colleagues have calculated the probability that their finding is a fluke to be five-tenths of a percent, or 2.8 sigma in particle physics parlance.
“It’s not an exact science yet, unfortunately,” Collar said. “But with the information we have, the usual set of assumptions that we make about the halo and these particles, their behavior in this halo, things seem to be what you would expect.”
Other dark-matter experiments, including Xenon100, have not detected the seasonal signal that CoGeNT and DAMA have reported.

The struggle to determine the nature of reality still marches on....

www.physorg.com
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reply to post by Maxmars


It's strange that WIMP is becoming synonymous with "dark matter" more and more frequently in the news. I don't understand the gnat analogy as dark matter passes through solid objects. We have tons of them passing through Earth everyday.

I think what they aren't allowing room for is the observational factor. Even on an electron level, matter acts as both wave and particle, depending on its observed status. What the heck do they think will happen when we finally "observe" dark matter?!