Thursday, November 4, 2010

Has Fermilab Discovered The Source of Dark Matter ? (4th family of neutrinos)

Physics experiment suggests existence of new particle

November 2, 2010

( -- The results of a high-profile Fermilab physics experiment involving a University of Michigan professor appear to confirm strange 20-year-old findings that poke holes in the standard model, suggesting the existence of a new elementary particle: a fourth flavor of neutrino.

The new results go further to describe a violation of a fundamental symmetry of the universe asserting that particles of antimatter behave in the same way as their matter counterparts.

Neutrinos are neutral born in the radioactive decay of other particles. The known "flavors" of neutrinos are the neutral counterparts of and their heavier cousins, muons and taus. Regardless of a neutrino's original flavor, the particles constantly flip from one type to another in a phenomenon called "neutrino flavor oscillation."

An electron neutrino might become a muon neutrino, and then later an electron neutrino again. Scientists previously believed three flavors of neutrino exist. In this Mini Booster Neutrino Experiment, dubbed MiniBooNE, researchers detected more oscillations than would be possible if there were only three flavors.

"These results imply that there are either new particles or forces we had not previously imagined," said Byron Roe, professor emeritus in the Department of Physics, and an author of a paper on the results newly published online in .

"The simplest explanation involves adding new neutrino-like particles, or sterile neutrinos, which do not have the normal weak interactions."

The three known types of neutrino interact with matter primarily through the weak nuclear force, which makes them difficult to detect. It is hypothesized that this fourth flavor would not interact through the weak force, making it even harder to find.

The existence of sterile neutrinos could help explain the composition of the universe, said William Louis, a scientist at Los Alamos National Laboratory who was a doctoral student of Roe's at U-M and is involved in the MiniBooNE experiment.

"Physicists and astronomers are looking for sterile neutrinos because they could explain some or even all of the dark matter of the universe," Louis said. "Sterile neutrinos could also possibly help explain the matter asymmetry of the universe, or why the universe is primarily composed of matter, rather than antimatter."

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