Bread, backpacks and bosons — a summer at CERN


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

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

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

The Yale students’ job was to analyze subatomic particle test collisions, look for specific particles such as Z bosons and J/Psi particles, and create visual displays of the collisions. The job involved an intensive amount of physics knowledge, computer coding, and graphics expertise.

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

Their visit coincided with the 10e anniversary of the discovery of the Higgs boson, a fundamental particle of the order of the electron or the quark, a historic moment celebrated by CERN scientists in July. In the same month, CERN announced the discovery of three new particles – a pentaquark and two tetraquarks – using a more powerful accelerator beam.

Event displays created by Yale students, which illustrated specific particle collisions, were an important part of the announcement.

It was an exciting time to be at CERN, and these students were at the heart of the experiment,” said Demers, Research Associate at CERN, collaborator of the ATLAS experience at the LHC, and a member of the international research team that discovered the Higgs boson (along with fellow Yale physicists Keith Baker and Paul Tipton).

I’m incredibly impressed with what they’ve accomplished,” 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 quartet of physicists from Yale College arrived in Switzerland in May, with a variety of scientific skills and research interests.

Haslund-Gourley, a native of Santa Barbara, Calif., has been passionate about physics since elementary school. She had already completed an internship in physics at Fermilab, in the suburbs of Chicago, and she hosts a scientific podcast, “Extended Office Hours”, on Spotify.

Thomas, originally from suburban Atlanta, studies physics and mathematics, with a particular interest in using geometric and topological machine learning methods to explore particle physics.

Gainey, like Haslund-Gourley, grew up in Santa Barbara. She had already worked in three science labs during her time at Yale – two of them were labs focused on astronomy research and one worked on particle physics. His research interests focus on the application of data science techniques to both fields.

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

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

They arrived at their rented apartment outside Geneva during pouring rain in the third week of May. Their excavations were only 10 minutes by train from CERN.

With Demers in the lead, they quickly got to work.

This magical land

Yale undergraduates entered the CERN stage amid a flurry of activity. The Large Hadron Collider, first launched in 2008, was entering its third extended series of particle collisions with a series of test collisions.

Their mission was two-fold: to select interesting collision “events” from the first data that would indicate whether the detector was working properly and to develop visual displays of these events, showing particles and energy deposits from the accelerator.

They spent weeks familiarizing themselves with the operation of the Large Hadron Collider itself, then familiarizing themselves with the computer tools they would use to access test data and write code to identify candidates for a collision event. .

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

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

On July 5, students were on site for the first collisions using the collider’s “stable beam,” which reached a breakthrough energy level of 13.6 TeV (tera electron-volts). They watched a collision live stream, listened to music, and waited to run their code.

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

It was kind of exciting pressure,” Thomas said. “They needed the event postings ASAP.”

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

It was incredibly validating,” Haslund-Gourley said.

A job well done

By all accounts, the work of the group has been crowned with success.

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

In addition to the projects assigned to them, the students said they enjoyed being immersed in an intense scientific environment away from home. Haslund-Gourley, for example, said she was inspired by the international nature of collaborations at CERN; Thomas was happy to have had the chance to meet some of the physicists he idolized from “Particle Fever,” the 2013 documentary film that inspired him to pursue physics in the first place.

The students had a snack while hiking in the mountains.
The students had a snack while hiking in the mountains.

During their off hours, the students hiked in the Jura Mountains, visited rustic villages in France, and explored the sights of Vienna, Budapest, Munich, and Bern. There were also plenty of opportunities to sample local cuisine.

A lot of bread was eaten,” Gainey said.

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

Haslund-Gourley, for her part, has been inspired by 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’s got the research bug. “I never felt stressed,” he said. “We all just hung around, did our thing and made it work. I know that I will continue to work at CERN for my thesis.


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