UChi: Dark–matter search plunges physicists to new depths

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UChi: Dark–matter search plunges physicists to new depths

Post by bystander » Thu Aug 12, 2010 12:24 am

Dark–matter search plunges physicists to new depths
University of Chicago | 11 Aug 2010
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This month physicist Juan Collar and his associates are taking their attempt to unmask the secret identity of dark matter into a Canadian mine more than a mile underground.

The team is deploying a 4–kilogram bubble chamber at SNOLab, which is part of the Sudbury Neutrino Observatory in Ontario, Canada. A second 60–kilogram chamber will follow later this year. Scientists anticipate that dark matter particles will leave bubbles in their tracks when passing through the liquid in one of these chambers.

Dark matter accounts for nearly 90 percent of all matter in the universe. Although invisible to telescopes, scientists can observe the gravitational influence that dark matter exerts over galaxies. ... Likely suspects for what constitutes dark matter include Weakly Interacting Massive Particles (WIMPS) and axions. Theorists originally proposed the existence of both these groups of subatomic particles to address issues unrelated to dark matter. ...

SNOLab will be the most ambitious in a series of underground locations where Collar and his colleagues have searched for dark matter. In 2004, they established the Chicagoland Observatory for Underground Particle Physics (COUPP) at Fermi National Accelerator Laboratory.
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The COUPP collaboration consists of scientists from UChicago, Fermilab and Indiana University at South Bend. In 2008 the collaboration released its first results that established an old technology of particle physics—the bubble chamber—as a potential dark–matter detector.
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Collar continually seeks underground venues for his research in order to screen out false signals from various natural radiation sources, including cosmic rays from deep space. ... The troublesome underground radiation sources consist of charged particles that lose energy as they traverse through a mile or more of rock. But rock has no impact on particles that interact weakly with matter, such as WIMPS, thus the move to Sudbury.

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neufer
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SNO-LLAB

Post by neufer » Thu Aug 12, 2010 2:07 am

http://en.wikipedia.org/wiki/PICASSO wrote:
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<<The PICASSO (Project In CAnada to Search for Supersymmetric Objects) experiment is searching for direct evidence of dark matter. It is located at SNOLAB in Canada. It uses bubble detectors with Freon [C19F4] as the active mass. PICASSO is predominantly sensitive to spin-dependent interactions of Weakly Interacting Massive Particles (WIMPs) with fluorine atoms. A bubble detector is a radiation sensitive device that uses small droplets of superheated liquid that are suspended in a gel matrix. It uses the principle of a bubble chamber but since only the small droplets can undergo a phase transition at a time, the detector can stay active for much longer periods than a classic bubble chamber. When enough energy is deposited in a droplet by ionizing radiation the superheated droplet undergoes a phase transition and becomes a gas bubble. The PICASSO detectors contain Freon droplets with an average diameter of 200 µm. The bubble development in the detector is accompanied by an acoustic shock wave that is picked up by piezo-electric sensors. The main advantage of the bubble detector technique is that the detector is almost insensitive to background radiation. The detector sensitivity can be adjusted by changing the temperature of the droplets. Freon-loaded detectors are typically operated at temperatures between 15 °C and 55 °C. PICASSO reports results (November 2009) for spin-dependent WIMP interactions on 19F. No dark matter signal has been found, but for WIMP masses of 24 GeV/c2 new stringent limits have been obtained on the spin-dependent cross section for WIMP scattering on 19F of 13.9 pb (90% CL). This result has been converted into a cross section limit for WIMP interactions on protons of 0.16 pb (90% CL). The obtained limits restrict recent interpretations of the DAMA/LIBRA annual modulation effect in terms of spin dependent interactions.
http://www.cwrl.utexas.edu/~bump/E603B/web/Brette/lapinagile.html wrote:
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<<Steve Martin’s _PICASSO_ addresses a simple question: what would have happened if Picasso and Einstein were to have met in a bar in Paris in at 1904? The entire play takes place within the bar. In the course of an hour and a half, Martin reconciles the right brain (art, represented by Picasso) and the left (science, represented by Einstein).

Shortly after the play begins, Einstein walks into the bar. He is 25, smartly-dressed, and can quickly do complicated calculations in his head. He “registers notions” in a patent office by day and works on his theories by night. He came to the bar to meet with a woman. When she finally arrives, they discuss gravity and other forces. By all accounts, he seems to be a very clean-cut, intelligent, scientific young man; he clearly represents the left brain. Picasso, on the other hand, has shaggy, disheveled hair, an untucked shirt, and a very dramatic air about him. He feels things deeply and quickly goes from being very happy to very sad. He is preceded by a one-night stand that he had two weeks ago. She retells a bit of that night, and says that he suddenly became preoccupied with an idea, but that it couldn’t be named—he just saw it. He mentions multiple times that he often can’t stop thinking about his different ideas. Picasso sees and feels things very deeply, but he sometimes has trouble verbally expressing his ideas (since they “can’t be named”). He’s very artistic and very right-brained.

For much of the first half of the play, Picasso and Einstein seem to be very much at odds. They have totally different occupations, treat women differently (Picasso is a bit of a womanizer whereas Einstein is more gentlemanly), and seem to have entirely different outlooks on life. There is actually a sequence where they fight back and forth over whose craft is more worthwhile. This ends when Picasso shouts “mine touches the heart,” to which Einstein cries “mine touches the mind!” They stand off, as though in an old Western film, and draw at 10 paces. Picasso scribbles a sketch while Einstein writes E=mc2. Each claims that theirs is more beautiful and perfect. Einstein explains that when physicists come up with new ideas, the most beautiful is usually right, and that they are just looking at the universe in new ways and describing what they see. Einstein realizes that that’s basically what he does when he draws. When Einstein and Picasso come up with new ideas, they both think it, draw or write it, and have a clear vision. That’s how they formulate the new concepts that will “bend the twentieth century,” as Einstein says. They imagine the impossible and bring it into being. In juxtaposing the posterchildren, so to speak, of modern art and modern physics, Martin brings the left and right brains together. He shows that new ideas—no matter what field they’re in—require the same sort of creative process. He reconciles the two halves of the brain and finds the parallels between them. He also seems to make the point that neither type of genius is any better than the other. Einstein is no more of a genius than Picasso just because he came up with the Special Theory of Relativity instead of Cubism, or vice versa. They are really much more similar than most people realize.>>
Art Neuendorffer

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Re: UChi: Dark–matter search plunges physicists to new depth

Post by owlice » Thu Aug 12, 2010 3:49 pm

Einstein realizes that that’s basically what he does when he draws.
That should read "Picasso realizes..."

IIRC, Martin majored in philosophy.

Sounds like an interesting play.
A closed mouth gathers no foot.

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