August 16, 2011

New Experiment Could Help Shed Light On Antimatter

A new Chinese experiment could help explain why matter predominates over antimatter in the universe.

The Daya Bay experiment aims to explain the mystery by using antineutrinos as a probe to measure a crucial type of transformation called neutrino mixing.

"Right now there is not a good understanding of what causes the matter-antimatter imbalance in the universe," Karsten Heeger, a University of Wisconsin"“Madison physics professor and one of the leading scientists in the experiment, said in a press release.

"We live in a world of matter and don't know where all the antimatter went."

Neutrinos come in three varieties: electron, muon, and tau.  These varieties can morph from one form to another as they travel through space and matter. 

Two of the oscillations have been studied but one transformation of electron neutrinos has not been measured before.

Neutrinos and antineutrinos can pass through something as large as a planet with no interactions due to them being tiny and uncharged.

The large size and sensitivity of the detectors in the Daya Bay experiment should give the best chance for researchers to collect enough antineutrinos to precisely measure the last unknown neutrino mixing angle.

"The results will be a major contribution to understanding the role of neutrinos in the evolution of basic kinds of matter in the earliest moments after the Big Bang, and why there is more matter than antimatter in the universe today," co-spokesperson Kam-Biu Luk of the US Department of Energy's Lawrence Berkeley National Laboratory said in a press release.

The antineutrino detectors are positioned underground and submerged in pools of ultra pure water to help shield them from cosmic rays, natural sources of radiation, and other background signals.

The experiment will consist of eight 125-ton antineutrino detectors in three different locations.

"By having these different locations, we can see the neutrinos at different distances from the reactors and how they change as they travel through space," Heeger said in a press release.

Several countries are involved in the Daya Bay Reactor Neutrino Experiment, including the U.S., China, Russia, the Czech Republic, Hong Kong and Taiwan.


Image 1: The Daya Bay Reactor Neutrino Experiment captures faint flashes of light that indicate antineutrino interactions in detectors filled with scintillator fluids. Each detector is lined with photomultiplier tubes. Two detectors have begun collecting data, two more have been completed, and four are under construction. (Photo by Roy Kaltschmidt, Berkeley Lab Public Affairs)

Image 2: The detectors now taking data are housed in the experimental hall nearest the two Daya Bay reactors, shown as the water pool in which they are submerged had been completely filled and before the pool was covered with a sliding roof, instrumented to identify incoming cosmic rays. (Photo by Joseph Y.K. Hor)


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