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Last modified: Monday, May 4, 2009

After delays, IU scientists now full-ahead on $278 million neutrino project

Matter-antimatter relationship to be studied with high-speed underground particle beam

May 4, 2009

BLOOMINGTON, Ind. -- They may be traveling through solid rock at about 200 miles per millisecond, but Indiana University's Mark Messier and a team of 180 other physicists hope that by keeping a close eye on those fast-moving neutrinos they may find an answer to one of particle physics' longstanding quandaries: Why do the most elementary particles have the mass that they do?

Messier, an associate professor in the IU College of Arts and Sciences' Department of Physics, watched Friday (May 1) as the first shovelful of dirt was turned on a $278 million project designed to explore the mysterious behavior of neutrinos, one of the most abundant subatomic elementary particles in the universe.

image of scientists

Photo by Chris Meyer

Some of the team of IU scientists and technical staff working on a $278 million U.S. Department of Energy neutrino project are, clockwise from left, Stuart Mufson, Luke Corwin, Jon Urheim, Jonathan Paley, Fritz Busch, Bob Armstrong, Mark Messier and Brian Baptista. They are standing beside a prototype component of the liquid scintillator that will be used to collect light from subatomic particle interactions.

Print-Quality Photo

A billion times more abundant than the particles that make up all stars, planets and people, neutrinos have been found to have mass, to pass through ordinary matter virtually undisturbed while traveling near the speed of light and to carry no electrical charge. They are so unique that scientists now contemplate whether neutrinos hold the answer to why the Big Bang produced more matter than antimatter.

After a funding cutoff nearly shut the project down two years ago -- scientists were able to keep working with carryover funds but no new federal money -- the international team of researchers that includes 16 scientists and technical staff from IU feared the slowdown could lead to a project shutdown.

"After a year of waiting and wondering we are very excited about getting started," said Messier, co-spokesman on the NOvA experiment. "Now the question we're all asking ourselves is, 'How fast can we go?'."

The answer: Probably not as fast as the 500 miles in under three milliseconds that neutrinos will travel as they pass through earth and rock from Fermilab in Illinois to the far detector facility in northern Minnesota, where ground was broken -- but the project team of physicists, scientists and technical staff are ready to see construction on the NOvA experiment begin.

NOvA stands for the NuMI (Neutrinos at the Main Injector) Off-Axis Electron Neutrino Appearance detector facility, a University of Minnesota laboratory about 40 miles southeast of International Falls, Minn. NuMI is the facility at Fermilab where protons are used from the main injector accelerator to produce an intense beam of neutrinos.

Because scientists still don't know the masses of the different neutrino types, or which type of neutrino is the lightest and which is the heaviest, the NOνA experiment is designed to search for oscillations of muon neutrinos to electron neutrinos by comparing the electron neutrino event rate measured at the Fermilab site near Chicago with the electron neutrino event rate measured at a location just south of International Falls, about 500 miles away. If oscillations occur, the far site will see the appearance of electrons in the muon neutrino beam produced at Fermilab.

"The NOvA detector's most critical element is the liquid scintillator, which comprises 70 percent of the total detector mass and is used to collect light from the particle interactions in the detector," Messier said. "Led by Stuart Mufson, IU's primary responsibility has been the optimization of the scintillator cost and performance, working out the mixing and delivery mechanism, and understanding how to ensure uniform standards of production quality."

The project, supported primarily through the U.S. Department of Energy, involves about 180 scientists and engineers from 28 institutions in seven countries, and a prototype detector is expected to be in use next year, with completion of the actual detector planned for 2014. A 200-ton detector will be used at the Fermilab near detector site and a 15,000-ton far detector will be housed underground in northern Minnesota.

The far detector will be composed of 385,000 cells of extruded PVC plastic. Each cell is 3.9 cm wide by 6.0 cm deep and is 15.5 meters long. The cells are filled with 3.3 million gallons of liquid scintillator, a material that becomes luminescent from ionized radiation, and scintillation light will be guided to photo-detectors using wavelength shifting fiber.

That is when Messier and the other scientists hope to observe the oscillation of muon neutrinos to electron neutrinos and in turn possibly understand the ordering of neutrino masses. Based on those findings, the physicists may be able to determine what the symmetry may be between neutrinos and antineutrinos.

Members of the IU group supporting NOvA, in addition to Messier and Mufson, include professors Jon Urheim and James Musser, senior scientist Charles Bower, post-doctoral researchers Jonathan Paley, Masaki Ishitsuka (now at Tokyo Institute of Technology) and Luke Corwin, graduate students Robert Armstrong and Nathan Mayer, technical staff Fritz Busch, Mark Gebhard, Brice Adams and Philip Childress, and IU Cyclotron Facility engineers Gerard Visser and Walter Fox.

To speak with Messier or other IU physicists, astronomers or technical staff on the NOvA project, please contact Steve Chaplin, University Communications, at 812-856-1896 or