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Blair Seidlitz, now a postdoctoral researcher at Columbia University, studied near-collisions of nuclear beams at the Large Hadron Collider in Switzerland, and he did so despite having severely limited vision

Blair Seidlitz, who earned his PhD in physics in 2022 from the �鶹��Ƶ, has won the Dissertation Award in Hadronic Physics for his dissertation, the society announced.

Seidlitz’s dissertation research was on the of the Large Hadron Collider, hosted at the international CERN laboratory in Switzerland. His CU Boulder research group, led by Professors Dennis Perepelitsa and Jamie Nagle, works in experimental nuclear physics—it collides nuclear beams (“ions") at the LHC to study the fundamental forces of nature under extreme conditions.

The major advance of Seidlitz’s dissertation was to use these nuclear beams at the LHC in an unusual way. “He was interested in the processes not where the beams slam into each other … but instead the cases where the beams just barely miss each other,” Perepelitsa said.

CU Boulder physics PhD alum Blair Seidlitz won the American Physical Society (APS) Dissertation Award in Hadronic Physics for his dissertation research on the ATLAS Experiment of the Large Hadron Collider.

“It turns out that in these cases, a photon emitted by one ion can strike the other, and thus result in rare and unusual ‘photo-nuclear’ collisions …. The ATLAS detector was not set up to take this kind of data by default. So Blair had to do a lot of work to develop the ‘trigger’ (the algorithms that decide which data to even record), to get access to this rare dataset.”

Perepelitsa said this kind of work is unusual for a graduate student; many graduate students work with existing infrastructure or use well-established procedures in research like this. “But Blair really took his idea from the conception stage, to implementing it himself, and helping to deploy it in person during data-taking at CERN,” a bustling scientific community at which Seidlitz spent significant time.

Once Seidlitz had collected the data, he then did a very careful analysis, which necessitated developing some new methods because nobody had really done this kind of thing before, Perepelitsa added.

The surprising result was that these sparse “photo-nuclear” collisions exhibited a collective “flow” behavior among their produced particles—“something you might only expect in the collisions of large nuclei where there are many, many particles that are produced and interact.”

“His measurement has come at a time when the scientific community is asking big questions, such as: Just how few particles can one have to still exhibit many-body collective motion? Blair’s thesis work, by paving the way to experimentally access these unusual datasets, is addressing these open questions head on!”

Seidlitz is now a post-doctoral researcher at Columbia University. He still works at ATLAS, but he now also works at a new experiment at the Relativistic Heavy Ion Collider, in which Perepelitsa and Nagle’s group at CU is closely involved. “So we are pleased that we can continue to collaborate with Blair very closely,” Perepelitsa said.

Seidlitz said he hopes to build on his graduate school work. “There are actually distinct categories (or types) of photon-nucleus collisions. My thesis work did not sort the different types, but studied them as a whole. In principle, it should be possible to sort these, although it has never been done. That way, we could study the ‘flow’ properties of each type individually, which would be really interesting.”

Seidlitz said that he and his colleagues will be able to study these types of collisions at the Electron Ion Collider, which is scheduled to be completed in the 2030’s at Brookhaven National Laboratory (BNL) on Long Island, New York.

Seidlitz said he was surprised to win the APS dissertation award. “They called me while I was in the sPHENIX control room (an experiment at BNL). I don't usually pick up my phone, but it seemed to not be spam, and as fate would have it, it was an official from APS saying I had won.”

Seidlitz has charted a successful academic career even though he has Stargardt's disease, a rare form of macular degeneration that leaves him with approximately 1/20th the visual acuity of average people.

A wheel in the ATLAS detector of the Large Hadron Collider. Blair Seidlitz's dissertation research focused on near-collisions of nuclear beams in ATLAS. (Photo: )

His vision posed many challenges, he said. “I guess the first challenge was learning as much as I could and getting through courses without being able to see the black board or projector, where I did most of my learning through textbooks.”

Seidlitz said disability service centers at CU Boulder and at his undergraduate institution, the University of Wisconsin, Madison, “really made it possible for me to succeed, from scanning old textbooks to make PDFs, to scanning students' homework so I could grade it when I was a TA and recommending assistive technology.” 

Another challenge was finding a field of research that would work for him. “Because physics that revolves around particle accelerators is so big and complicated, large collaborations are formed and the work is shared. Some people build the detectors—something I could not do—and others set up data analysis and reconstruction, which is a lot of software to take the signals from individual detectors and turn it into a measurement of a photon with a particular momentum, for example,” Seidlitz explained, adding:

“This is something I can do! I would say there are still challenges day to day, but they are manageable, and I am very grateful that I am in a place where I can contribute and do valuable work.

Seidlitz grew up in Wisconsin and earned a BS in engineering physics from the University of Wisconsin, Madison. As an undergraduate, he conducted research in plasma physics with Cary Forest, applying optical emission spectroscopy techniques for measurements of the electron temperature in the Plasma Couette Experiment and the Madison Plasma Dynamo Experiment.

The American Physical Society is a nonprofit organization working to advance and diffuse the knowledge of physics through its research journals, scientific meetings and education, outreach, advocacy and international activities.

APS represents more than 50,000 members, including physicists in academia, national laboratories and industry in the United States and throughout the world.

Top image: The eight toroid magnets surrounding the calorimeter in the ATLAS detector. The calorimeter measures the energies of particles produced when protons collide in the center of the detector. (Photo: )

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