Team including LSU scientist finds neutrinos can transform

The Advocate

By Josh Noel

December 8,2002

It turns out the sun is just fine. It was the understanding of solar physics that needed repair.

An LSU physicist may have helped answer a long-standing question about the sun with a finding announced Friday: the neutrinos streaming from the sun -- the smallest, simplest particles known in the universe -- change identity en route to Earth.

One previous theory held that the sun might burn out too soon.

Instead, a 90-member team including LSU physicist Bob Svoboda submitted their more-optimistic findings to Physical Review Letters, a weekly physics journal. Svoboda expects it to be published within two weeks.

"A lot of texbooks are going to have to be rewritten," said Svoboda, 50, a 12-year veteran of the LSU physics department. "Us experimental physicists love nothing more than proving an existing theory wrong."

After dozens of trips over more than three years of study in the Japanese mountains, Svoboda called the announcement "the light at the end of the tunnel," even though observation will continue for two more years.

Neutrinos, billions of which pass through every square inch of space every second, are unimaginably minute particles of uncharged energy escaping from nuclear reactions such as the sun, stars or man-made nuclear reactors.

They were first conceptualized and named -- roughly to mean "little neutral one" -- in the 1930s, but were not proven to exist until 1956, by Fred Reines, a Nobel Prize winner from the University of California, Irvine.

Because measurements of neutrinos escaping the sun rarely equaled the number predicted by existing theory, physicists suspected one of three scenarios: either they didn't understand the sun, they didn't understand the neutrinos, or something catastrophic was happening -- like the sun was going to flame out.

"Though I don't think anyone of repute actually believed that," Svoboda said. "But quite a few people believed that maybe exotic particles were cooling the sun just a little. That would reduce the number of neutrinos."

Instead, Svoboda and the team of physicists from more than a dozen universities (including a handful of LSU students) concluded that the neutrinos change "flavors" as they leave the sun.

Three types of neutrinos were already known to exist. Now it is proposed that they can change type between the sun and the earth.

"It's like, if you look at your pet at breakfast and it's a cat, then at lunch it's a dog, then at dinner it's a cat again," Svoboda said. "That's what neutrinos were doing, oscillating like that. It was startling when people first this because it's not something you see in everyday life, where something is one thing, then it's something else later."

In the project, called KamLAND, the neutrinos are studied in a two-story high plastic balloon buried a half-mile in the ground. The balloon, filled with baby oil, is suspended inside a steel tank filled with a lighter baby oil. The plastic balloon is only two hundredths of a centimeter thick and holds 1,000 tons of baby oil.

Svoboda's job has been to coordinate construction and calibration of the machine.

The hundreds of thousands of calculations about neutrino interactions are studied on Super Mike, and LSU supercomputer named for Gov. Mike Foster.

Data from the experiment is fed into Super Mike by Steven Dazeley, 35, who moved to Baton Rouge from Australia three years ago to work on the project. Svoboda said he hired Dazeley from a thick stack of applicants.

"I was interested in astronomy when I was a kid and I'd heard of the lack of neutrinos and I was kind of fascinated from way back," said Dazeley, who has a doctorate in gamma ray astronomy from the University of Adelaide. "Now, most of the hard work is done."

Svoboda said he became interested in neutrinos as an undergraduate student at Florida State University. The interest was reinforced when he operated a nuclear reactor on a submarine during his six years in the Navy.

"I was told that 10 to 15 percent of the power was going out of the reactors in neutrinos and couldn't be had back," he said. " I found that interesting."

He studied with Reines, who discovered neutrinos, in the mid-1980s at the University of California, Irvine just after earning his doctorate.

Svoboda said the elusive nature of neutrinos has inspired a subculture, as evidenced by the dozens of neutrino sites on the Internet. Svoboda even claims to have heard of a rock band from Seattle called The Neutrinos.

"I'd like to get their CD," he said. "But I haven't seen it around here."