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PHYSICS SEMINAR ANNOUNCEMENT
Swenson College of Science and Engineering
Department of Physics
University of Minnesota Duluth
"What the carbon nucleus looks
like to a neutrino"
Dr. Richard Gran,
Department of Physics and Astronomy,
University of Minnesota Duluth
Tuesday, December 1, 2015
Abstract:To the neutrino, the carbon nucleus is not just the sum of its parts; it looks like MORE than just six protons and six neutrons. New analysis of MINERvA experiment data reveals specific contradictions with decades old, simple models for neutrino-nucleus interactions. If those simple models are an awful description of the data, then the most modern models that incorporate multi-nucleon effects could be said to achieve poor to sorta-good agreement. Current and future neutrino oscillation experiments will depend on still more improvements to understanding these neutrino interactions. They areexpected to be the driving uncertainty for our ability to measure oscillation parameters and explore for exotic properties of the universe like matter/anti matter asymmetry. This measurement was pioneered by UMD M.S. students John Demgen and Ethan Miltenberger.
"High-energy physicists have a reputation for being jerks," said Dr. Alec Habig, who was lured from Boston to UMD in 2000 to head up cutting-edge physics experiments at the Soudan Underground Laboratory.
But Takaaki Kajita of Japan and Arthur B. McDonald of Canada "are two of the best people you can imagine," Habig said.
Kajita and McDonald shared the prize, announced Tuesday, for their game-changing discoveries about the mysterious world of neutrinos, subatomic particles that outnumber everything else in the universe except for light particles.
Habig has been part of that world since 1996, when as a postdoctoral student he joined a research team led by Kajita and Ed Kearns, a Boston University physicist, spending about a third to half of his time in Japan. There, Kajita led work at the Super-Kamiokande detector -- built in an abandoned mine -- to seek the answer to what Habig calls the "big question."
The question had been bugging physicists since the 1960s.
The Nobel committee that bestowed the prize explained it like this: "Scientists had theoretically calculated the number of neutrinos that were created in the nuclear reactions that make the sun shine, but when carrying out measurements on Earth, up to two-thirds of the calculated amount was missing. Where did the neutrinos go?"
Takaaki ultimately won the Nobel Prize for the answer he proposed in 1998, Habig said. The neutrinos didn't disappear at all, he found, but fooled observers by changing identities -- from one of three "flavors" to another.
Physicists know that for a particle to change it has to be traveling slower than the speed of light, Habig explained. And if it's traveling slower than the speed of light, it must have some substance, some "mass."
McDonald's Nobel Prize was given because he was the one who discovered that neutrinos have mass -- confounding previous expectations.
Habig and his team are working to take those conclusions to the next step at the neutrino detector in the Soudan lab and now at a second underground detector near the Ash River, 30 miles southeast of International Falls. They're studying neutrinos fired underground, directly from the Fermi National Accelerator Laboratory near Chicago.
They're studied underground because "on the surface, regular cosmic rays are lighting you up pretty good," Habig said.
Kajita and McDonald "built a strong scaffold" upon which further investigation of neutrinos can be built, Habig said.
"If we don't figure out what they're doing or how they behave, our grandchildren won't have the information to assemble a more useful picture," he said.
The study of neutrinos today is comparable to electrons when Michael Faraday was studying them in the 1800s, Habig said.
Neutrinos are much more common - a billion of them for every proton or electron or neutron, Habig said. But they are also "really hard to study."
Other than the fact that "he's an extremely nice guy," Habig said he knows little of Kajita's life outside the laboratory. In Japan, Habig said, "work and personal life cross far less than they do in the U.S."
He told of two Japanese students working on the neutrino project who didn't discover they had the same first name until they wrote a paper together.
Although bestowing a Nobel Prize in 2015 for a discovery made in 1998 is actually considered a quick turnaround, Habig said he wasn't surprised by the announcement.
"It was an important enough discovery," he said. "It's satisfying that they got the right guys."
To read the article at Duluth New Tribune please follow the link:http://www.duluthnewstribune.com/news/3855097-umd-physicist-connected-nobel-prize-winners
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