There was a lot going on at the home of the Large Hadron Collider this summer.
A new particle was discovered. ICARUS, a 60-foot-long detector built to search for an elusive (and possibly non-existent) particle, was shipped out on a six-week voyage to its new home outside Chicago at Fermilab. And a weasel chewed through a power cable — again! — knocking an ion collider offline.
A contingent of William & Mary students was there for it all: Kevin Nelson ’18, Sydney Ostrom ’20, Devin Moore ’19, plus Lauren Liegey, a graduate student in the university’s Department of Physics. The group worked and studied this summer at CERN, the European high-energy physics facility renowned as the site of the discovery of the Higgs boson.
Kevin Nelson was at CERN as a participant in the University of Michigan’s Research Experience for Undergraduates (REU). The others accompanied William & Mary Physics Professor Jeff Nelson to CERN. The CERN group is part of a larger William & Mary contingent of a large, multi-national collaborative working on the Long-Baseline Neutrino Facility/ Deep Underground Neutrino Experiment (LBNF-DUNE).
Other William & Mary members of the LBNF-DUNE collaborative, working stateside on the experiment, are Michael Kordosky and Patricia Vahle, both associate professors of physics, postdocs Alex Radovic and Edgar Valencia, graduate student Luis Zazueta Reyes, recent graduate Ciaren Buteux ’16 and Will Henninger, the machine shop director in the physics department.
For the students at CERN, the day is divided between lectures and work on various projects, including a prototype for a neutrino detector to be used in LBNF-DUNE, which is scheduled to go online in 2026.
“Every day starts at 9:15 when we attend a few summer student lectures that CERN puts on,” Ostrom said. “The lectures are all about different aspects or theories involved in high-energy, particle, nuclear — or really any kind of physics that take place at CERN.”
After lunch in the CERN cafeteria, it’s time to get to work. Their prototype will influence the design and construction of the actual instrument to be installed at DUNE. It will receive a beam of neutrinos sent from Fermilab 800 miles through the earth to the DUNE site deep beneath the surface of South Dakota.
Kordosky explained that the experiment is designed to measure a value in neutrinos. Neutrinos are shape-shifting particles created by numerous sources, and scientists believe an understanding of neutrino behavior can help to answer a number of long-standing fundamental questions of science. (See Neutrinos…and Why We Study Them at William & Mary.)
The students are working on a prototype of the far detector, the neutrino-catching apparatus that will be assembled underground at the DUNE facility in South Dakota. Moore explained that the team is working on a part of the prototype far detector called the field cage module. Actual construction was held up for a few weeks while the team waited for parts to arrive.
“Today we started receiving the parts for constructing it,” Moore wrote in a July 18 email from CERN. “We'll begin by assembling the various modules, then attaching and testing the electrical components on it. We'll be helping with this process, but it will continue once we've returned to the states.”
Even if actual construction of the prototype was delayed by the wait for parts, the students at CERN weren’t idle. They were pressed into service tracking progress of the elusive prototype detector parts and assigned other important and necessary tasks for the construction of the detector, which will rely on argon gas cooled and condensed to liquid form.
“When we aren't tracking down crates or contacting packing companies, we essentially run tests on different sets of equipment to make sure that they will work properly when they are actually installed,” Ostrom explained. “For example, we've run a lot of tests on the dual-phase detector to check that there are no holes in the welding that would allow gas to leak out.”
Kevin Nelson was involved in the ICARUS project, as well. ICARUS, another liquid-argon neutrino detector, was at CERN for refurbishment after beginning its experimental life at an Italian physics lab. The detector was shipped across the Atlantic to Fermilab, where physicists hope it will resolve the mystery of the “sterile neutrino,” a much-debated particle whose demonstrated existence — or lack thereof — will allow scientists to move more confidently down one path or high energy physics or another. Nelson arrived just in time to wave goodbye to ICARUS — and to get an important assignment related to the journey.
“On my first day at CERN we shipped ICARUS to Chicago,” he said, explaining that the detector was equipped with accelerometers to track the bumping and jostling the instrument received during the long voyage.
“My job was to write code to remove ‘fake’ signals from the dataset that were induced if the accelerometer itself was bumped and not the ICARUS detector,” a frequent occurrence, he explained. “When we read data off the sensor, we plug a cable into the sensor, effectively bumping the sensor and not the detector. Many of these so-called ‘fake’ signals require somewhat sophisticated signal processing to analyze, distinguish and remove from the dataset.”
The students are fully aware of being part of the community and culture that is part of the CERN experience. A rising sophomore, Ostrom pronounced herself particularly lucky to be able to participate in a summer experience that’s usually reserved for upperclass and graduate students.
“The first week that we were here, on July 4, it was the fifth anniversary of the discovery of the Higgs boson — which was discovered right here at CERN's LHC detector!” she said. “I actually remember when I was just about to start my freshman year of high school in the summer of 2012, my dad told me about the discovery because he knew that I was interested in science. It was pretty cool to realize that I was listening to lectures in the same auditorium where the discovery was first announced.”
She added that being a full-fledged, even if temporary, member of the CERN family carries certain perks, including being among the first to hear about the Large Hadron Collider’s “beauty experiment’s” discovery of the new particle, a baryon that is made up, appropriately, of two charm quarks and an up quark.
“Getting that announcement in an email seemed to make all three of us at least a little more excited to be working here than we already were,” Ostrom added. Moore seconded, pronouncing the announcement “probably the most exciting thing that happened while we were here.”
Nelson had an opportunity to meet a couple who are generally regarded as living embodiments of the traditions and history of CERN.
“The coolest moment from my summer so far was when I met Maria and Giuseppe Fidecaro on the tram from CERN to Geneva. Maria and Giuesspe have worked at CERN since its beginnings and they still do to this day,” Nelson said.
He explained that some of his friends recognized the Fidecaros from a tour of the Synchrocyclotron facility, where the couple began work at CERN 60 years ago.“They were such nice people and were clearly excited to see a new generation of physicists so passionate about working at CERN,” Nelson said. “They still eat lunch almost every day in the CERN cafeteria, so it's said that you don't work at CERN until you've bumped into them.”