ATLAS award recognizes dissertation work investigating quark-gluon plasma

In the world of particle physics research, the people who study “nuclear physics” are a minority—a little bit quark-y, you might say. 

“Our field is slightly different,” says Kurt Hill, a 2020 PhD graduate in physics from the University of Colorado Boulder.

Consider that the Large Hadron Collider at CERN (the European Organization for Nuclear Research) near Geneva, Switzerland, reserves 11 months of the year for researchers interested in what happens when protons collide, and just one month for “nuclear” types who are more interested in colliding “heavy ions,” the nuclei of atoms, such as lead, composing many protons and neutrons, to study the mysterious substance known as quark-gluon plasma. 

During his time at CU Boulder, Hill was advised by Dennis V. Perepelitsa and Jamie Nagle, professors in the CU Boulder physics department, whose research is funded by grants from the U.S. Department of Energy. He also conducted research at CERN during the “nuclear” month of November for three years running, 2016 to 2018. Based on that work, he presented his dissertation, “Investigations of p+Pb Collisions at Perturbative and Non-Perturbative QCD Scales,” in April 2020. 

And now, Hill’s dissertation has been chosen as one of eight recognized by the ATLAS Collaboration—one of four major experiments ongoing at CERN—for its 2020 ATLAS Thesis Awards. 

“Only Kurt works on the somewhat more exotic ‘nuclear physics’ side, so it is a big deal for his work to be recognized at this level by the particle physics community,” says Perepelitsa. “He’s also one of only two recipients from a university in the U.S.—the other is from Berkeley.”

Hill, who grew up in Walnut Creek, California, earned bachelor’s degrees in physics and mathematics from the University of California, Davis, before taking time off to travel in Europe and Asia. When the time came to apply for graduate school, CU Boulder was his first choice, based on several factors.

“CU checked all the boxes. I love mountain biking and skiing,” he says. “And the (nuclear physics) research group I was eyeing is highly regarded in the field,” he says.

Hill also enjoyed spending time at CERN each fall.

“It’s this big central lab where everybody is kind of focused. All the people from different scientific efforts in this one place, the primary place in the world for this type of physics research—it was really cool,” he says. “There is a kind of buzz there. Everybody is doing exciting things.”

What Hill was doing, specifically, was researching what happens when you collide protons with lead to “probe the nucleus of lead.” Protons are made of quarks, held together by gluons, and mapping out particles emitted from such collisions advances the understanding of what’s going on inside a nucleus.  

“That sounds like a simple thing, but with these small particles, it’s highly complicated, due to quantum mechanical effects,” Hill says. “When you make these collisions, small droplets of quark-gluon plasma are generated, and that’s a primary goal, to study that plasma.”

He uses an analogy to describe quark-gluon plasma as a kind of liquid water, compared to protons and neutrons, which are more like ice—“It’s so hot and dense that protons and neutrons have melted and can’t really exist,” he says.

Despite his early success in nuclear-physics research, Hill decided to leave the academic world after graduation to pursue other interests. 

“I couldn’t really see myself as a professor as my main job, and even though I liked (nuclear physics), I didn’t think I should invest the effort in a (postdoctoral fellowship) if I didn’t see myself going all the way,” he says. 

He now works as a software engineer for Pyka, an Oakland-based company that makes fixed-wing, autonomous electric airplanes used for crop-spraying.

“I do miss getting to collaborate with all these really interesting people from all over the world on a regular basis,” he says. “But I had an opportunity to work with cool people on something exciting. To get to do something new is always attractive to me.”