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New piece found in subatomic puzzle

Research scientists say they have identified the missing piece of a major puzzle involving the makeup of the universe by observing a neutrino particle change from one type to another.
Image: Magnetic spectrometer
The OPERA experiment at Gran Sasso in Italy uses huge magnetic spectrometers such as the one shown here to detect the particles given off by neutrino interactions.OPERA
/ Source: Reuters

Research scientists say they have identified the missing piece of a major puzzle involving the makeup of the universe by observing a neutrino particle change from one type to another.

The CERN physics research center near Geneva, relaying Monday's announcement from the Gran Sasso laboratory in central Italy, said the breakthrough was a major boost for efforts at its own Large Hadron Collider to unveil key secrets of the cosmos.

According to physicists at Gran Sasso, after three years of monitoring multiple billions of muon neutrinos beamed to them through the earth from CERN, 456 miles (730 kilometers) away, they had spotted one that had turned into a tau neutrino. Behind that scientific terminology lies the long-sought proof that the three varieties of neutrinos — subatomic particles that with others form the universe's basic elements — can switch appearance, like the chameleon lizard.

The discovery is important, scientists say, because it helps explain why neutrinos arrive at earth from the sun in apparently far smaller numbers than they should under the Standard Model of physics that has held sway for 80 years.

Shedding light on dark matter
The fact that neutrinos are now proven to switch identities — as posited by two Moscow scientists in the late 1960s based on earlier work by a U.S. physicist — suggests that other types of neutrinos could exist but slip detection.

That insight in turn could help shed light on the nature of dark matter — an as-yet-unseen type of matter that makes up about a quarter of the universe.

Only about 4 percent of the universe's matter-energy content is directly observable. The rest is composed of dark matter and another mysterious, invisible component known as dark energy.

"This is really exciting because it shows that there are things beyond the Standard Model," CERN spokesman James Gillies said. CERN is the French acronym for the European Organization for Nuclear Research, a facility that straddles the border between Switzerland and France.

Beyond the LHC
The search for concrete evidence of dark matter and a determination of what it might be is part of the research program for CERN's Large Hadron Collider, the world's biggest scientific machine. But the beaming of muon neutrinos to the Italian center is not part of the LHC experiment. The beam is directed south under the Alps from another, smaller, CERN particle accelerator.

CERN quoted Lucia Votano, director of the Gran Sasso laboratories, as saying that experiment in Italy had achieved its first goal. Gran Sasso is 70 miles (112 kilometers) south of Rome, near the town of L'Aquila,which was hit by a devastating earthquake in April last year.

Scientists are confident that the detection in the center's OPERA experiment of a tau neutrino would be followed by other discoveries showing that neutrinos can change, Votano said.

Work on the behavior of neutrinos already brought a Nobel Prize to the late U.S. scientist Ray Davies, who first recorded in the 1960s that fewer neutrinos were coming from the sun than current theories of the universe predicted.

He shared the prize in 2002, at the age of 87 and four years before his death, with fellow U.S. researcher Ricardo Giacconi and Japanese physicist Masatoshi Koshiba for the contribution to astrophysics.