Crash course: UC physicists hunt for antimatter in Japan's new particle collider

The physics professors at the University of Cincinnati are determined to unlock the mystery of antimatter as part of an international team working on a particle collider at the Japanese High Energy Accelerator Research Organization. The accelerator called SuperKEKB propels electrons and positrons in opposite directions around a tunnel at nearly the speed of light so they collide in a spectacular annihilation that generates pure energy.

But it all occurs at a phenomenally small scale — so small that the collisions are measured in nanobarns. A barn is a whimsical name created in 1942 during the Manhattan Project to describe the comparatively large area of the nucleus of a uranium atom (as big as the broad side of a barn).

And when the particle collider begins its experiments in months to come, its detector called Belle II will record as many as 50 billion of these collisions in fine detail, capturing so much data that it has to be measured in petabytes — or 1 million gigabytes. And the research group has plans to expand that capacity a thousandfold to exabytes by next year.

“Each event contains less than a megabyte of data, but you get 50 billion of them. It adds up,” Kinoshita said.

Kinoshita is hoping the collisions will tell her more about antimatter, which is a byproduct of these particle annihilations.

“Each annihilation is in a state of perfect matter-antimatter symmetry,” Kinoshita said.

Kinoshita became a physicist like her father, Toichiro Kinoshita, a professor emeritus at Cornell University and member of the National Academy of Sciences. Toichiro Kinoshita calculated the precise magnetic property of the electron and muon, another elementary particle, in a career that began at the University of Tokyo during World War II.

While her father is a theoretical physicist, UC’s Kinoshita gravitated to experimental physics. She has bachelor’s and master’s degrees in physics from Harvard University and earned a doctorate at University of California, Berkeley.

“I always wanted to be a scientist,” she said.

Schwartz joined physicists at Japan's particle accelerator in 2002 after conducting experiments at particle labs around the world: the DESY synchrotron in Germany, the CERN proton-antiproton collider in Switzerland, the Brookhaven National Laboratory proton accelerator in New York and at Fermilab’s accelerator outside Chicago.

“Probably the biggest question is trying to figure out why we live in a matter universe instead of an antimatter one,” Schwartz said. “Everything that exists could have been made up of anti-protons and anti-electrons, anti-molecules — and anti-people.”

Antimatter behaves like matter except for the opposite electrical charge of its protons and electrons.

“Nature is giving you these hints, pieces of a puzzle,” Schwartz said. “You have to think about what each of those pieces tells you about the puzzle.”

New technology is opening up research questions that experimental physicists had little hope of answering decades ago. Theoretical physicists, too, have made huge strides in helping explain the matter-antimatter paradox, Schwartz said. He plans to make regular trips to Japan over the next five years as part of his research collaboration. The project promises to give UC students plenty of opportunity to publish original research, he said.

“Certainly in terms of technology, it is a very good time to be an experimental physicist,” Schwartz said. “We’ve taken all the easy measurements. Now we’re taking the hard measurements.”

Belle II’s collider generates far more luminosity — or particle collisions — than the lab’s previous collider, allowing researchers to collect about 50 times more data. The ultimate goal is to look for new evidence to explain why matter prevails over antimatter.

“With 50 times as much data, you can probe more rare things than we could before,” UC’s Kinoshita said. “You may say, ‘That’s great — 50 times as much!’ But it’s only 50 times as much. It may take 1,000 times as much data to observe CP violation.”

The discovery of evidence explaining this paradox, called CP violation, earned Japanese physicists Makoto Kobayashi and Toshihide Maskawa a 2008 Nobel Prize.

“The main goal of Belle II is to look for new physics beyond the ‘Standard Model’ of particle physics,” Schwartz said. “We are convinced there is another type of CP violation out there because the CP violation discovered by Kobayashi and Maskawa is not enough to convert the universe from 50 percent matter and 50 percent antimatter to the 100 percent matter we observe today.”

UC’s researchers were at the sprawling lab in Tsukuba (about 45 minutes north of Tokyo) in April when the team conducted its first successful collision. Now researchers will refine the acceleration and detection systems before experiments begin.

The collider itself is a masterpiece of precision engineering, Sandilya said. It fires electrons and positrons in opposite directions around a circular tunnel nearly two miles around to collide at an impact point 50 nanometers by 10 microns – or roughly the size of a chromosome.

“Colliding a beam that size over 3 kilometers is an engineering marvel,” Sandilya said.

Access is strictly controlled for safety reasons to prevent exposure to deadly ionizing radiation.

Now the UC physicists are looking forward to collecting and analyzing data with an international team of collaborators.

“I’m from India. My affiliation is the United States. And I’m working on an experiment in Japan. Here, you feel more like a world citizen,” Sandilya said.

Japan’s particle accelerator is the first new collider built since the Large Hadron Collider at CERN in Switzerland in 2008. But while CERN has a high-energy accelerator that smashes protons with other protons, Japan’s fires electrons at positrons.

“When you use protons versus protons, there are leftover particles so it’s messy,” Kinoshita said. “But as far as we know, the electron is truly a fundamental particle.”

The collisions create particles that are of particular interest to researchers: B Mesons and anti-B Mesons composed of quarks. UC’s research is funded by the U.S. Department of Energy to explore these subatomic particles, she said.

“The reason we get funding is to look for what we call ‘new physics,’” Kinoshita said. “There is a list of particles: We know what they are. There is a list of interactions:  We know what they do. But we think there are interactions yet to be discovered. And some of our findings so far are mysterious. So those are the corners we concentrate on.

“It’s a big team effort. I am confident we’ll get answers.”