IU-built scintillator ‘in the game’ as NOvA experiment detects its first evidence of oscillating neutrinos

An Indiana University professor who is co-lead scientist on a major, multi-institutional investigation into the mysterious behavior of the subatomic particles known as neutrinos recently announced the project’s first results before an international gathering of colleagues.


Mark Messier of IU, right, and Young-Kee Kim, former deputy director at Fermilab, during the construction of the NOvA detector in 2012.

Mark Messier, a professor in the IU Bloomington College of Arts and Sciences’ Department of Physics, delivered the address at the 2015 Meeting of the American Physical Society’s Division of Particles and Fields today in Ann Arbor, Mich.

The results are part of the $278-million NOvA project, an international collaboration of nearly 210 scientists and engineers from 39 universities, laboratories and institutions around the world. The experiments were conducted in partnership with Fermilab, a massive particle accelerator near Chicago funded by the U.S. Department of Energy.

“Scientists on the NOvA experiment saw their first evidence of oscillating neutrinos, confirming that the extraordinary detector built for the project not only functions as planned, but is also making great progress towards its goal of a major leap in our understanding of these ghostly particles,” said a statement released from the lab this morning.

Neutrinos come in three forms: muon neutrinos, electron neutrinos and tau neutrinos. The experiment whose first results were reported today seeks to answer a major mystery in modern physics: what causes neutrinos to transform – or “oscillate” – from one form to another? The principles that govern the oscillation of a muon neutrino into an electron neutrino, when solved, could hold new clues to the origins of the universe.


The far detector measures roughly 200 feet long, 50 feet high and 50 feet wide and is made of PVC filled with a scintillating oil. Photo courtesy Fermilab.

“IU’s involvement in the project has been extensive,” said Messier, who has worked on the project since it’s inception nine years ago. “IU’s major responsibility was to deliver three million gallons of the liquid scintillator that is the heart of the experiment.”

A material of mostly mineral oil and psuedocumene that becomes luminescent from ionized radiation, the scintillator fluid comprises an important part of NOvA – also known as the NuMI Off-Axis Electron Neutrino Appearance far detector building — whose physical structure and detection software were also partially designed by IU scientists.

A 14,000-ton, multi-story structure the size of several football fields, NOvA is located on a remote patch of land owned by the University of Minnesota in Ash River, Minn. The neutrinos created for the experiment are generated at Fermilab, located in Batavia, Ill., and then beamed instantly through the Earth to the detector over 500 miles to the northwest.

Neutrinos pass through matter as though it doesn’t exist. Although still poorly understood, neutrinos are the most abundant particles with mass in the universe.

“These results show that NOvA is ‘in the game,'” Messier said. “Even though we’re just getting started, we’re getting results of comparable quantity to other similar experiments around the world due to the excellent performance of the beam and detector.”


A pivoting machine used to move each block of the detector into place is now part of the completed structure. Photo courtesy Fermilab.

Other IU scientists playing an important part in NOvA are Stuart Mufson, professor in the Department of Astronomy; Jim Musser, professor in the Department of Physics; and John Karty, associate scientist in the Department of Chemistry, all of whom have served in a variety of roles related to the scintillator system. Mark Gebhard, a master technician, is responsible for coordinating efforts to monitor and test the system. Jon Urheim, professor of physics, has also contributed to the project.

Other IU contributors are Michael Baird, Gavin Davies, Hayes Meritt, Evan Niner and Denver Whittington, who are postdoctoral fellows, and Teresa Lackey, Ryan Murphy, Fernanda Psihas and Justin Vasel, who are graduate students.

In addition, Niner will join Fermilab as a postdoctoral fellow this fall. He and Baird will deliver thesis defenses based on their work on NOvA in IU’s Swain Hall on Monday, Aug. 10, and Friday, Aug. 14, respectively.

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