Is the origin of the universe hidden in the particle collision data?

Yen-Jie Lee arrived at MIT as a graduate student in 2006, which was a bit of a culture shock. The aspiring particle physicist had studied physics at National Taiwan University before his career took a break in the forested mountains of Taiwan. There, he worked as a lieutenant in the Marine Corps to fulfill the military service required by the nation. He still remembers the deafening crackle of artillery drills and the unyielding pressure of daily military life. Towards the end of his service, Lee applied for doctoral programs, including several in the United States. When he visited MIT, he felt an immediate relationship with physics professor Wit Busza. As a graduate student in Busza's group, Lee had the opportunity to go to Geneva during a pivotal moment in particle physics.

There, scientists were preparing to ignite the Large Hadron Collider, the largest and powerful particle accelerator of the world. The collisions of particles produced by the LHC were expected to produce conditions similar to the early universe and perhaps entirely new and unpredictable phenomena. Lee found himself at the center of the analysis team, where he quickly learned to communicate with other scientists, in the English language and in the equations of physics. Eventually he helped measure and interpret some of the LHC's early collisions.

"There were several thousand collaborators, everyone was interested in this physics and I was one of the first to understand the data," says Lee. Since those early days, Lee has continued to search for clues to the beginnings of the universe, using data from the LHC. At MIT, where he is now an associate professor of physics, he is looking for models and interactions in the extreme consequence of particle collisions that could tell us something about how the universe was born. These experiments could also reveal the inner workings of other extreme environments, such as neutron stars.




"I had a lot of fun with this very simple system" , says Lee, who based his undergraduate and masters theses on data from the Belle experiment. "It made me want to learn the law of nature and whether we can find new physics and new phenomena involving particle detection".


Lee was keen to probe the fallout from heavy ion collisions, even though initial experiments involved less complicated collisions at the time between protons. Lee was positioned on the research team to write the first physics paper reporting the results of these initial proton-proton experiments.

The LHC began performing its first heavy ion experiments towards the end of Lee's PhD, and was able to analyze some of the early data from these long-awaited races. Through these analyzes, he discovered fast-moving quarks produced in collisions, crawling through the resulting plasma, in jets.

"It's like looking at a bullet fired through water," says Lee. "We can see the trail that follows the bullet and we can use it to know the propagation of the sound of the water. It's the same with these jets, where we can use quarks to know the sound of the early universe ".