Physicists probe atomic mystery

June 4, 2012 at 7:25 PM
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PASADENA, Calif., June 4 (UPI) -- U.S. physicists say the most sensitive measurements yet in a hunt for a hypothetical atomic process could help solve some of the universe's biggest mysteries.

Researchers at the California Institute of Technology and Stanford University's SLAC National Accelerator Laboratory say their experiment, involving the radioactive decay of atomic nuclei, could help scientists understand the fundamental laws of physics and why there is more matter than antimatter -- and therefore why regular matter like planets, stars and humans exists at all.

The EXO-200 experiment has made the most sensitive measurements on the nature of a hypothetical so-called neutrinoless double beta decay, and has narrowed the range of possible masses for the neutrino -- a tiny uncharged particle that rarely interacts with anything -- passing through rock, people and planets as it zips along at nearly the speed of light, a Caltech release reported Monday.

In a normal double beta decay, which was first observed in 1986, two neutrons in an unstable atomic nucleus turn into two protons. In the process, two electrons and two anti-neutrinos -- the antimatter counterparts of neutrinos -- are emitted.

Physicists have suggested two neutrons could also decay into two protons by emitting two electrons without producing any anti-neutrinos if the two neutrinos produced could somehow cancel each other out.

If this neutrinoless process does indeed exist, physicists would be forced to revise the Standard Model, the remarkably successful theory that describes how all elementary particles behave and interact, because the model does not predict a neutrino could act as its own antiparticle.

"People have been looking for this process for a very long time," EXO-200 researcher Petr Vogel said. "It would be a very fundamental discovery if someone actually observes it."

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