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Neutrino experiment for
Daya Bay (click image for larger view.)
"Neutrinos are very hot right now," said Brookhaven National Laboratory physicist Laurence Littenberg, a Daya Bay collaborator. "It was only in the last decade that we learned they have mass, and there's still so much that we don't know about them."
Uncharged elementary particles produced naturally from the sun and cosmic rays, neutrinos morph, or oscillate, among three flavors — electron, muon, and tau — as they travel through space, people, buildings, and even Earth itself, interacting only rarely. Scientists have characterized two of these oscillations in detail, and are seeking to measure details of the third. The Daya Bay project is poised to measure an important property of this oscillation, possibly helping scientists gain a better understanding of the early history of the universe.
One of the most perplexing questions has to do with the matter that makes up the universe — and everything and everyone in it. The Big Bang should have created equal amounts of matter and antimatter, which would have annihilated each other. Yet today, the universe is almost entirely matter. Some scientists believe that this puzzling phenomenon is tied to the properties of neutrinos.
"At the moment, we don't know why the universe is dominated only with matter," said Lawrence Berkeley National Laboratory physicist Kam-Biu Luk, one of two scientific spokesmen for the Daya Bay project. "It's the reason that everyone and everything exists. This is very exciting and important, and I would love to be part of the team that finds out why we are here."
The Daya Bay experiment would look for the third type of neutrino oscillation by studying antineutrinos produced in nuclear reactions at a power station containing a cluster of several reactors in southern China. Detectors described as "liquid onions," because of their layered design, will sit beneath granite mountains at different distances from the reactors. Scientists will compare the number of electron antineutrinos produced in the reactors and the number expected to arrive at each detector to how many events are actually detected to get a measure important for understanding this oscillation.
The U.S. and China will share leadership and responsibilities for Daya Bay. "The U.S. and China have been trying to get more and more scientific exchanges between them, and this is another step in that direction," says Randy Johnson, DOE's program director for the Daya Bay project.
The project leaders hope to pass through a series of critical decision steps as quickly as possible to start construction in 2007, with data collection beginning in 2010.
Submitted by DOE's Brookhaven National Laboratory
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