W&M Professor, Students Help Catch Neutrinos

Local researchers are part of an international effort to understand ghostly particles that might explain why the universe includes planets and matter, instead of a volatile mix of destructive gases.

You might have heard of subatomic particles called protons, which have a positive charge, and electrons, which have a negative charge.

But there are also neutrinos, which have no charge. They're the lightest pieces of matter known — 10 million times lighter than an electron — and so tiny in mass, they challenge scientists' understanding of mass itself.

Neutrinos pass through most things without interacting with them. That posed a great challenge for Jeff Nelson, a physics professor at the College of William and Mary. He helped build a neutrino detector in a Minnesota mine as part of a $178 million experiment called MINOS, or Main Injector Neutrino Oscillation Search.

A continuous underground beam of neutrinos travels 450 miles from the Fermi National Accelerator Laboratory outside Chicago to the detector in northern Minnesota's historic Soudan iron mine.

Neutrinos are so unobtrusive, the mine's detector will pick up only a tiny fraction of the particles beamed its way during the next five years, Nelson said. "We're going to produce a billion trillion neutrinos in the experiment," he said. "We'll have 10,000 of these things seen over five years."

About 200 physicists and students from 33 universities in six countries are taking part in the experiment, interacting mostly through the Internet.

Nelson and his students helped build another neutrino detector at Fermilab last year. They use computers to simulate what happens in the detector and compare it with real data from the experiment.

The work will help answer fundamental questions such as: Why do things have mass? How do neutrinos contribute to the fact that the universe is mostly matter, instead of a gaseous equilibrium of matter and anti-matter?

For more information, visit www-numi.fnal.gov.

Radiation Blockers

In September 2002, local health officials started distributing potassium iodide pills to people who live and work within 10 miles of the Surry Power Station. The pills could prevent thyroid cancer by blocking the accumulation of radioactive iodine in the body, in the event of a nuclear accident or terrorist attack.

Researchers at William and Mary and Jefferson Lab recently used the same concept to protect laboratory mice while studying how radioactive compounds accumulate in different organs. Their experiment triggered yet-to-be-answered questions about the recommended human dose of potassium iodide.

Scientists fed potassium iodide to the mice, anesthetized them and injected a radioactive compound. They used a Jefferson Lab-built imager to observe how different organs accumulated the radioactive substance over time.

This method helps researchers study how the body processes potentially harmful substances and a wide variety of compounds, including hormones.

Scientists scaled down the human dose of potassium iodide to a mouse-sized portion. But that dose didn't adequately protect the mice. It didn't prevent significant accumulation of the radioactive compound.

Researchers found that five times the scaled-down human dose was needed, said Eric Bradley, a biologist at William and Mary.

"Out of it comes the question: Does this have implications that perhaps the dose for humans is not adequate? From the data we have, there's no way to answer the question."

The metabolism of mice is different from that of humans, which might answer why the scaled-down dose didn't work. The William and Mary scientist team — including Bob Welsh, Margaret Saha and students William Hammond and Jianguo Qian — have discussed doing another experiment on larger animals, such as rats.

Bradley stressed that now was way too early to reach conclusions about the human dose.

"I do think it is important, though," he said. "It's a human health issue."

— Contact Dave Schleck at 247-7430 or via e-mail at dschleck@dailypress.com. *