Bread, backpacks, and bosons — a summer at CERN

Caitlin Gainey and some of her Yale friends spent summers in Europe hiking mountains, strolling through medieval villages — and looking for subatomic particle collisions few people have ever seen.

Gainey, a Yale College senior studying astrophysics, along with fellow Yale seniors Dawson Thomas, Matthew Murphy, and Alexandra Haslund-Gourley, conducted critical research at one of the world’s most important physics centers – the Large Hadron Collider at CERN (the European Nuclear Research Organization), just outside of Geneva, Switzerland. They were part of a science team led by Sarah Demers, a physics professor in Yale’s Department of Arts and Sciences.

The Large Hadron Collider – the world’s largest particle accelerator, housed in a vast underground facility – returned to service in mid-summer after four years of modernization. Physicists use the facility to test theories about the fundamental laws of physics, from the composition of space and time to the connection between quantum mechanics and general relativity.

The Yale students’ task was to analyze test collisions of subatomic particles, look for specific particles such as Z bosons and J/Psi particles, and create visual representations of the collisions. The work required an intense amount of physics knowledge, computer programming and graphics expertise.

An example of the particle collision event displays created by Yale students, based on data from CERN's Large Hadron Collider.

An example of the particle collision event displays created by Yale students, based on data from CERN’s Large Hadron Collider.

Her visit coincided with the 10thth Anniversary of the discovery of the Higgs boson, a fundamental particle the size of an electron or quark, a milestone celebrated by CERN scientists in July. In the same month, CERN announced the discovery of three new particles – a pentaquark and two tetraquarks – with a more powerful accelerator beam.

A prominent part of the announcement were event displays created by the Yale students that illustrated specific particle collisions.

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It’s been an exciting time to be at CERN, and these students were right in the thick of it,” said Demers, a CERN associate research scientist, collaborator on the ATLAS experiment at the LHC, and part of the international research team that discovered the Higgs boson (along with the Yale physicists Keith Baker and Paul Tipton).

I’m incredibly impressed with what they’ve achieved,” she said.

Alexandra Haslund-Gourley, Matthew Murphy, Dawson Thomas, Caitlin Gainey and Gianantonio Pezzullo
Left to right: Alexandra Haslund-Gourley, Matthew Murphy, Dawson Thomas, Caitlin Gainey, and Yale postdoctoral fellow Gianantonio Pezzullo.

meet the team

The Physics Quartet from Yale College arrived in Switzerland in May and have a diverse range of science skills and research interests.

Haslund-Gourley, who is from Santa Barbara, California, has been interested in physics since elementary school. She previously completed a physics internship at the Fermilab facility in suburban Chicago and hosts the science podcast “Extended Office Hours” on Spotify.

Thomas, who is from a suburb of Atlanta, is studying physics and mathematics and has a particular interest in using geometric and topological machine learning methods to explore particle physics.

Like Haslund-Gourley, Gainey grew up in Santa Barbara. She had already worked in three science labs during her time at Yale – two of which were labs focused on astronomical research and one worked in particle physics. Her research interest is the application of data science techniques to both fields.

Murphy, a member of the Yale rowing team from Portland, Oregon, had no previous lab experience before emailing Demers, his former professor in PHYS 200, to ask about research opportunities in her campus lab. She told him she could do it – or he could just come to Switzerland.

This was my first research,” Murphy said. “I didn’t know what to expect.”

They arrived at their rented apartment outside of Geneva in the third week of May during a heavy rainstorm. Their excavations were only a 10-minute train ride from CERN.

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Led by Demers, they quickly got to work.

This magical land’

Yale students entered the CERN scene amid a wave of activity. The Large Hadron Collider, which first became operational in 2008, started its third extended series of particle collisions with a series of test collisions.

Their task was twofold: to select from the early data interesting ‘collision events’ that would indicate whether the detector was working properly, and to develop visual representations of those events showing particles and energy dumps from the accelerator.

They spent weeks educating themselves about how the Large Hadron Collider worked, and then becoming familiar with computer tools they would use to access test data and write code to identify collision event candidates.

I remember sitting at the apartment with Dawson on a Friday night in mid-June, writing code that didn’t quite work,” Murphy said. “Then suddenly it started working perfectly. It was fantastic.”

I felt so lucky,” Haslund-Gourley said. “I always grew up wanting to work at CERN, that magical land where physicists learn about the forces and particles that make up the universe.”

On July 5, students witnessed the first collisions with the collider’s “stable beam,” which reached a world-breakthrough energy level of 13.6 TeV (teraelectron volts). They watched a live stream of collisions, listened to music—and waited to run their code.

When we started, it was a race against time, with some of the best physicists in the world reviewing everything we were doing,” Gainey said.

It was an exciting kind of pressure,” said Thomas. “They needed the event displays as soon as possible.”

One of their first visualizations was used almost immediately in a scientific paper for the 2022 International Conference on High Energy Physics. It was actually the first slide in the presentation.

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That was incredibly empowering,” said Haslund-Gourley.

A job well done

The group’s work was reportedly successful.

Our students identified the only publicly available candidates for ATLAS event displays, and they were regularly thanked and highlighted in collaboration-wide presentations,” said Demers.

Aside from their assigned projects, the students said they enjoyed immersing themselves in an intense, academic environment away from home. For example, Haslund-Gourley said she was inspired by the international nature of the collaboration at CERN; Thomas was glad he got the chance to meet some of the physicists he idolized from Particle Fever, the 2013 documentary film that inspired him to get into physics in the first place.

The students grabbed a snack during a hike in the mountains.
The students grabbed a snack during a hike in the mountains.

In their free time, the students hiked in the Jura mountains, visited rural villages in France and explored the sights in Vienna, Budapest, Munich and Bern. There was also ample opportunity to taste the local cuisine.

A lot of bread was eaten,” Gainey said.

As for the future, Gainey said she will continue her CERN work at Yale this year and make it the basis of her senior project. Thomas, meanwhile, thinks he’s found an “accidental” way to apply topological methods of machine learning to particle physics.

For her part, Haslund-Gourley was inspired by the data science and machine learning techniques used to process collision data at CERN and hopes to apply similar analysis techniques to neurological data.

And Murphy? After a summer at CERN, he says he has the research fever on a grand scale. “I never felt stressed,” he says. “We were all just hanging out, doing our jobs and making it work. I know that I will continue to work at CERN for my thesis.”

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