Post image for NOvA experiment, IU physicists mark milestone

NOvA experiment, IU physicists mark milestone

April 11, 2013

Taking data from cosmic rays for the first time, the international NOvA experiment — with the fingerprints of Indiana University researchers all over it — began recording its first three-dimensional images last week, moving closer to the day  when physicists can begin measuring neutrino energies.

“We’re not measuring neutrinos yet, but this marks a milestone of the detector construction,” says Mark Messier, associate professor of physics in the College of Arts and Sciences at Indiana University Bloomington, who is also spokesperson for the NOvA experiment. “We are now running all our systems end-to-end for the first time and can begin calibrating the instrument for the first beam from Fermilab in June.”

Neutrinos are still mysterious to scientists: They come in three flavors, or types, and mass states; they oscillate, changing from one type to another; and they are more abundant than the cosmic rays that constantly fall on earth from space. In this  helpful video explaining the basics of the NOvA experiment, Messier observes that “neutrinos are everywhere.” They are the most abundant particle in the universe, he says, so much so that “16 million neutrinos from the sun pass through your thumbnail every second of every day and every night.”

Fermilab, America’s premier national laboratory for particle physics research located outside of Chicago, will start sending a beam of neutrinos 500 miles through the earth to the NOvA detector under construction in Ash River, Minn. The NOvA detector is huge — at 30 million pounds it’s the world’s largest PVC plastic structure. Its 385,000 PVC cells are being filled with 2.8 million gallons of IU-crafted liquid scintillator, a material of mostly mineral oil and psuedocumene that becomes luminescent from ionized radiation.

When a neutrino interacts in the NOvA detector, the particles it produces leave trails of light in their wake. The detector records these streams of light, enabling physicists to identify the original neutrino and measure the amount of energy it had. IU’s primary responsibility has been the optimization of the scintillator cost and performance, working out the mixing and delivery mechanism for the scintillating fluid, and understanding how to ensure uniform standards of production quality.

“I’ve basically spent a lot of time over the past decade inventing an industrial process to produce and transport liquid scintillator,” says IU Bloomington Profesor of Astronomy Stuart Mufson, whose research is tied to measuring neutrinos and anti-neutrinos. “Liquid scintillators were invented after World War II and used in different formulations in many high-energy physics experiments. However, none ever used nearly so much product. We developed the NOvA formula here and developed the ways to quality-control the product at production at a blender in Hammond, Ind., and at Ash River where it’s delivered.”

What governs neutrino change — what makes a muon neutrino oscillate into an electron neutrino — is a mystery that when solved could hold new clues to the origins of the universe. The three varieties of neutrinos — muon neutrinos, electron neutrinos and tau neutrinos — can morph from one to another through the process called oscillation. NOvA will measure one of these oscillations, muon to electron, using both neutrinos and anti-neutrinos — a key first step in identifying the subatomic processes that took place right after the Big Bang, physicists believe.

“If the Big Bang created equal amounts of matter and antimatter, corresponding particles of matter and antimatter would meet and annihilate one another,” Messier says. “But somehow we’re still here, and antimatter, for the most part, has vanished.”

Charge-parity symmetry theorizes that nothing would change about the laws of physics if every particle were replaced with its antiparticle, but it turns out that matter and antimatter are not mirror images, possibly explaining why they exist in unbalanced quantities. Breaking charge-parity symmetry is called CP violation, and to advance the theory that neutrinos tipped the balance between matter and antimatter, researches need to observe CP violation in action.

“By studying neutrino and antineutrino oscillation, we may be able to determine whether or not antineutrinos follow the same pattern as neutrinos when they change from one flavor to another. If they don’t, that would be a signal of CP violation,” Messier says. “The same mechanism that could cause neutrinos and antineutrinos to oscillate differently could have implications for the mechanism that would have led to an abundance of matter over antimatter in the early universe.”

Other IU researchers who work on the NOvA experiment, from liquid scintillator production to rapid feedback data acquisition systems, include IU physics professors James Musser and Jon Urheim; postdoctoral researchers Luke Corwin and Denver Whittington; graduate students Michael Baird and Evan Niner; IU physics technical staff Fritz Busch, Mark Gebhard, Brice Adams, Philip Childress, Brian Baugh and Rick Maloney; IU Cyclotron Facility engineers Gerard Visser and Walter Fox; and IU Department of Chemistry Mass Spectrometry Facility manager Jonathan A. Karty.

The $278 million NOvA experiment is an international collaboration of nearly 180 scientists and engineers from 34 universities, laboratories and institutions around the world, with the NOvA detector is under the operation of the University of Minnesota through a cooperative agreement with the U.S. Department of Energy’s Office of Science. Scientists are funded by the U.S. Department of Energy, the National Science Foundation, and funding agencies in the Czech Republic, Greece, India, Russia, and the United Kingdom.

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