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Marvin Marshak, physics professor

Twin Cities campus physics professor Marvin Marshak is part of a new international project to study neutrinos in northern Minnesota.

Video icon. To learn more about the impact of this project, watch the University News Service video.

University goes small-game hunting in far north

The Department of Energy gives the University $45.6 million for new neutrino project in northern Minnesota

By Deane Morrison

Nov. 2, 2007; updated Nov. 6, 2007

A lot of oil will soon be found underground in northern Minnesota. But nobody will be drilling for it. Instead, the University, armed with a new $45.6 million grant from the U.S. Department of Energy, will put it there as part of an international physics experiment to probe the origins of our Universe. The oil will serve as a target to catch neutrinos--vanishingly small, electrically neutral subatomic particles that were produced in huge numbers by the Big Bang and are still emitted by stars and the cosmic rays that rain down on Earth. Neutrinos are part of the mysterious invisible material called dark matter, which is believed to account for at least 80 percent of all the matter in the Universe. "If you want to completely understand the Big Bang, you need to know how neutrinos contributed to it," says physics professor Marvin Marshak, a lead investigator in the project. "We live in a sea of them. They constitute a second universe of sorts, weakly connected to ours." The project, called NOvA,* will involve about 200 scientists and engineers from 33 institutions in seven countries.

Mining MINOS

Neutrinos are so tiny that for many years, physicists doubted whether they had any mass at all. There are three types of neutrinos, and theory holds that if the different types can change into one another, or "oscillate," then they must possess mass.

MINOS neutrino detector
The new NOvA neutrino detector will be even bigger than the steel MINOS detector in the Soudan Underground Laboratory.

One experiment set up to answer the question about neutrino mass is MINOS, in which DOE's Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., shoots beams of neutrinos 445 miles through the ground to a detector in the University-operated Soudan Underground Laboratory in Soudan, Minn. The data so far confirm that neutrinos do oscillate during their journey and so must have mass. But while the Soudan detector catches neutrinos from the central axis of the beam, physicists are also interested in what goes on in off-axis parts of the beam, where neutrino oscillations are most likely to occur. The NOvA detector will be situated near the Canadian border in Ash River, about 40 miles southeast of International Falls and seven miles from the central beam axis.

"If you want to completely understand the Big Bang, you need to know how neutrinos contributed to it," says physics professor Marvin Marshak.

The detector, weighing in at a hefty 33 million pounds, will be housed in a building sunk 45 feet below ground. It will contain numerous plastic cells filled with mineral oil and a chemical that will emit light when a neutrino hits an atom in the detector. Given that neutrinos have no trouble zipping through the entire Earth without hitting a single atom, that will be a relatively rare event. "We think about a trillion neutrinos will pass through the detector in a year," says Marshak. "We may get 10 neutrino hits per day."

A Universe--luckily--out of balance

According to the current theory of the Universe, the Big Bang led to the production of 12 fundamental building blocks of matter, including the three types of neutrinos. But it also produced "twins" for all those particles out of a substance called antimatter, which reacts violently with matter. When a particle of matter collides with its antimatter twin, they annihilate each other, leaving only energy in their wake. That's what happened right after the Big Bang: The matter and antimatter particles collided, leaving nothing but energy--and a small amount of matter. Why the Big Bang produced a slight excess of matter over antimatter has puzzled physicists for decades. "One holy grail in physics is to answer the question 'What happened to antimatter?'" says Marshak. Fermilab will shoot beams of both neutrinos and their antimatter counterparts, called antineutrinos, through Soudan and on to Ash River. Differences in how the two particles oscillate may help solve the mystery of the missing antimatter. Whatever the answer, we can thank our lucky stars the excess of matter existed, because without it there would have been nothing from which to make stars, planets, or people. The off-axis neutrino oscillations are also expected to shed light on what happens during certain kinds of radioactive decay that involve loss of a neutrino from an atomic nucleus. One famous example is the radioactivity from carbon-14 used to date biological materials. Construction on the building will begin in fall 2008 and end in spring 2010, according to Marshak. After that, the detector will take two years to install. Besides Marshak, NOvA will use the talents of other physics professors, including Dan Cronin-Hennessy, Alec Habig at UMD, Kenneth Heller, Earl Peterson, Ronald Poling, Keith Ruddick, and Roger Rusack. Also key to the project is William Miller, supervisor for the University's labs at Soudan and Ash River. UMD's Richard Gran is involved in a neutrino project at Fermilab in Chicago. "This is a great example of how universities are an integral part of the Department of Energy's scientific research program," says Robin Staffin, senior adviser to the director of the DOE's Office of Science. "NOvA will be at the forefront of neutrino science in the next decade, but we would not be able to do it without outstanding research groups like the University of Minnesota."

*NuMI Off-Axis Electron Neutrino Appearance

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