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Rattling WIMPs.

Rattling WIMPs

Astronomers and physicists now have a number of interlockingreasons for believing that most of the universe--up to 90 percent--is made of matter that we can't see and that most likely is much more exotic than the stuff ordinary atoms are made of.

A candidate for the dark matter that is receiving a good dealof attention now among physicists is the class of hypotehtical subatomic particles called WIMPs, or weakly interacting massive particles. Blas Cabrera of Stanford University has developed a new class of particle detector that uses the acoustical effects of passing WIMPs on solid crystals to determine their presence.

The existence of WIMPs has not yet been directly demonstrated. Cabrera's experiment is intended both to demonstrate their existence and to show that they inhabit the universe in sufficient numbers to do what cosmologists want them to do: namely, make the universe close on itself.

Up to now, detectors for subatomic particles have generallyused either the particles' optical effects or electrical effects to determine their presence. WIMPs, being weakly interacting, almost never have these effects. However, WIMPs are massive--10 or more times as heavy as a proton--so, as they pass through a crystal of silicon, they can give an electron or an atomic nucleus a bump from which it will recoil. The bump becomes a vibration, called a phonon, that rattles along the lattice of the crystal. At the face of the crystal, the phonon will strike a superconducting aluminum tunnel junction, which will record its presence.
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Title Annotation:detector for weakly interacting massive particles
Author:Thomsen, Dietrick E.
Publication:Science News
Date:May 9, 1987
Previous Article:Regenerating neutrinos.
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