UT Researchers Help Solve Physics Mystery

KNOXVILLE — A University of Tennessee physicist has helped build a piece of equipment that is providing some answers about longstanding mysteries in the world of subatomic particles.

Standard scientific theories predict the sun should emit a certain amount of neutrinos, which are subatomic particles with almost no mass.

UT physics professor Dr. Bill Bugg is part of a team of scientists who reported in the journal Physics Review Letters that previous measurements of neutrinos emitted by the sun showed fewer particles than predicted.

Bugg said the new experiments suggest neutrinos can change their shape while traveling through space, thereby eluding older particle detectors and creating the numerical discrepancy.

But the new detector developed by the team can see these previously invisible particles, which add up to what was predicted in the computer models.

“The experiments are hard to do because they have to be deep underground to get rid of the effects of cosmic radiation,” Bugg said. “The neutrino detector is in an abandoned zinc mine in Japan 10,000 feet below the surface. The 4,000-ton machine we helped build records about two neutrino contacts per day.”

Bugg said researchers from UT provided parts for the detector that catches faint traces of neutrinos, which pass easily through solid matter.

“The tool we use in these detectors is a large mass of material that gives off light when charged particles pass through it,” Bugg said. “This light is detected by photo-multiplier tubes. There are 2,000 of these tubes in this experiment, and UT prepared about 600 of them.”

Solving the missing-neutrino problem will help scientists refine their basic theories about the nature of matter and the universe, Bugg said.