Scientists "99 percent" certain sterile neutrino doesn't exist

Scientists said Monday they are now "99 percent" certain that a hypothesized particle known as the "sterile neutrino" does not exist after analyzing two years' worth of data from an icy particle detector at the South Pole.

"Failing to detect the elusive particle ... means physics remains in the dark about the origin of the tiny neutrino mass, or why they have mass in the first place," Francis Halzen, principal investigator for the IceCube Neutrino Observatory, a massive detector embedded deep in the ice beneath Antarctica, said in a statement.

Neutrinos are ghostly particles with almost no mass and only rarely interact with matter. Trillions of neutrinos will course through your body in the time it takes to read this sentence.

There are three known types of neutrinos: muon, electron and tau. Hints of a possible fourth type of neutrino have come from several experiments. Known as the "sterile neutrino," the hypothesized particle would not interact at all with matter except, possibly, through gravity.

If discovered, the sterile neutrino would help explain a number of puzzles, such as the mismatch between matter and antimatter in the universe and the origin of dark matter.

The new study, published in the U.S. journal Physical Review Letters, included two independent analyses of data from the massive Antarctic detector -- each consisting of a year's worth of data or about 100,000 neutrino events.

The groups scoured the hundreds of thousands of neutrino events that reached the IceCube detector after coursing through the Earth from the sky in the northern hemisphere.

The search focused on neutrino events occurring in the 320 GeV to 20 TeV energy range. In this range, Halzen said, sterile neutrinos would produce a very distinctive signature.

However, the striking feature associated with the sterile neutrino was nowhere to be found, said Halzen, also a professor of physics at the University of Wisconsin-Madison.

As a result, they concluded that there is 99 percent certainty the sterile neutrino hinted at by previous experiments is not real. Enditem