Physicist gets rare staff position at CERN atom smasher

UO physics professor Tim Cohen has become the second researcher from a U.S. institution ever to join the staff at the European Organization for Nuclear Research theory group.

Cohen, a theoretical particle physicist, will travel to Switzerland this July to begin a six-year position at the organization, more commonly known as CERN. The CERN Theory Group consists of 20 staff members, most of whom are temporary.

Tim CohenCohen did not apply for the position. A casual phone conversation with a friend and colleague led to discussions among CERN higher-ups, who ultimately chose Cohen for the role because of his strong European connections and long list of publications.

Due to the length of his appointment, Cohen will pause most of his teaching responsibilities at the UO. However, he will stay connected with students in his research group, continue to collaborate on ongoing projects, and serve on thesis committees. As part of his position at CERN, Cohen has access to the organization’s visitor fund, allowing his students and postdoctoral researchers from the UO to visit during his time at the lab.

Interested students will be able to stay at CERN for up to a month at a time, with their expenses fully covered. Cohen said the organization has offered him what amounts to a few months’ worth of total financial support for students each year, meaning that the length of students’ covered stays may depend on how many students decide to come.

Oregon already has a strong presence at CERN, with a handful of UO faculty members stationed at its ATLAS experiment, a massive detector used to study tiny, high-energy particles. The UO also has postdoctoral researchers working in the experimental physics group permanently stationed at the European lab, as well as experimental particle physics students spending extended visits there.

Scientists in particle physics are divided between theorists and experimental physicists. Theorists like Cohen make predictions about the outcomes of interactions between subatomic particles based on established frameworks, while the experimenters design experiments to test those predictions and report their findings to the community.

If the outcomes of the experiments don’t match the predictions, theorists and experimenters work together to revise their predictions and devise new experiments to improve their understanding.

“One of the things I love about this field is that there’s this absolutely beautiful interplay between the theoretical community and the experimental community,” Cohen said.

At CERN, the theory group works to help interpret the immense volume of data collected by detectors along the Large Hadron Collider, the world’s largest particle accelerator. The immense machine forms a 17-mile ring hundreds of feet below the French-Swiss border, where CERN researchers use it to smash subatomic particles together, allowing them to investigate the mysterious properties of the building blocks of the universe.

Massive detectors are located along its circumference. As a postdoctoral researcher, Cohen had the chance to tour the 14,000-ton CMS detector and the 7,000-ton ATLAS detector, an experience he cites as one of the most profound of his career.

The detectors, located deep underground, have been used to search for extra dimensions, dark matter and the Higgs Boson an elementary particle whose discovery solidified the scientific understanding of what’s called the Standard Model of particle physics.

“The ingenuity is mind-boggling,” Cohen said. “And the fact that it works spectacularly, I find it extremely inspiring.”

Cohen’s work will focus on working through the data to locate gaps in the current understanding of the physical universe. By the end of his stay at CERN, Cohen hopes to have published new research papers with his European colleagues.

When not theorizing at CERN, Cohen will travel to Lausanne, Switzerland, where he’ll work with the theory group at the Swiss Federal Institute of Technology a few days each week. He’s moving to France in July, a time-consuming process he said has been made easier by the support he’s received from his UO colleagues.

“Everyone has been phenomenal,” Cohen said. “I am deeply grateful to all the wonderful folks in my department, research group and UO administration for supporting me in taking this position.”

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