Physics Bridges Long Distances to Study Tiny Particles

Neutrinos are everywhere.

These extremely tiny particles – many times smaller than the electrons that orbit individual atoms – are thought to play a role in everything from solar energy to radioactive decay to the “dark matter” that makes up most of the universe.

Neutrinos’ small size and the difficulty in isolating them for study has made it hard for physicists to fully understand how they relate to the other subatomic particles that form the building blocks of atoms and molecules. But an experiment being conducted by researchers from the University of Cincinnati and 17 other universities could unlock critical secrets about the nature of neutrinos.

“This is really basic research, but it’s important in that respect,” said

McMicken's 

Randy Johnson, professor of  

physics

, as he described the Booster Neutrino Experiment, known as  the MiniBooNE experiment, currently underway at the

Fermi National Accelerator Laboratory

 near Chicago.

In the mid 1990s, an experiment at Los Alamos National Laboratory suggested that neutrinos behave in ways that violate scientists’ theories about particle physics. Three types, or “flavors,” of neutrinos had been identified at that point, each associated with a specific type of subatomic particle. The Los Alamos experiment suggested that there might be a fourth flavor of neutrino, one that was immune to all known forces except gravity.

“A fourth flavor of neutrinos can’t come about in our normal physics,” said Johnson.

The MiniBooNE experiment was launched in 1997 to verify or disprove the Los Alamos findings, and UC researchers have been part of the program since its start. Johnson and his research team sourced the 250,000 gallons of ultra-pure mineral oil used to fill the experiment’s giant neutrino detector, and they continue to monitor the experiment's data stream.

“I, as an experimenter, have an interest in making sure my experiment runs correctly,” he said.

Johnson and his colleagues set up a remote workstation in October, which allows them to share the 24-hour duty of monitoring the experiment’s high-energy equipment. From two computers, McMicken physicists can monitor the experiment’s high-energy proton beam, 173,000-amp particle collector and the 36-foot diameter neutrino detector’s 1,550 sensors. Without the remote station, researchers would have to go to Chicago to participate in the experiment.

“What we’ve done here is opened the experiment up for more scientists to participate,” he said. “We have a lot of professors and graduate students who would like to take monitoring shifts.”

And along with providing a new research opportunity on campus, Johnson said the remote monitoring station has caught potentially experiment-damaging problems before they can derail the experiment. During the second week of remote monitoring, Johnson identified an error that had locked up a data-logging computer, and also spotted an error in the computer that guides the experiment’s high-energy photon beam.

“We were able to fix that in about 20 minutes,” he said of the second error, which could have let loose a stray beam of energy powerful enough to melt the experiment’s vital aluminum components.

The MiniBooNE experiment is scheduled to continue collecting data until June 2009, but already it has produced important results. Its data ruled out with 98 percent certainty the existence of the fourth flavor of neutrino that the Los Alamos experiment had suggested. But other results suggest that the three existing flavors of neutrinos may interact in ways not predicted by physicists.

For Johnson, that puzzling result is good news.

“That’s something that’s fun in any kind of experiment. You find something a little weird, and people come in and give you ideas about what it means,” he said. “That’s where the theorists come in. They’re going to have a great time figuring this out.”