The Hub of the Physics Universe
Indara Suarez and her students are building a detector that may help solve some of science’s biggest mysteries
By Marc Chalufour
One of the biggest collaborative science projects ever is buried underground outside of Geneva, Switzerland. More than 5,500 scientists, students, and staff from 54 countries have worked on the Compact Muon Solenoid Detector (CMS) at CERN, the European Organization for Nuclear Research—all trying to solve some of the biggest mysteries of the universe.
The detector provides clues to those mysteries by recording data from particle collisions—40 million per second—in the adjacent Large Hadron Collider (LHC), the world’s most powerful particle accelerator. The CMS, which is compact only in comparison to the 27-kilometer loop of the LHC, is located in an underground cavern and measures 94 feet long and 49 feet in diameter. Layers of sophisticated sensors and detectors fill the space.
“When we look at our universe, we don’t understand most of it—85 percent of all matter in the universe is dark matter, and we don’t know what that is,” says Indara Suarez, an assistant professor of physics and a longtime collaborator on the CMS.
The search for answers about dark matter and other fundamental questions has kept her coming back to CERN. At the same time, Suarez, a Mexican immigrant and first-generation college grad, wants to pass her enthusiasm on to a new generation of scientists. She engages undergraduates in her research in hopes of empowering historically underrepresented communities to pursue STEM careers—and their work at CERN could have a big impact.
Suarez and her students, most of whom are women and people of color, are in the midst of a multiyear effort to build upgrades for the CMS so it can record more data than ever and help scientists better understand the nature of—and maybe even the origins of—the universe.
Perfect Timing
Power supplies hum from workbenches along the walls of Suarez’s lab. Spools of red and black wire, green circuit boards, soldering irons, and glue guns litter the shelves and countertops. A string of colorful tissue paper flags with skulls cut out of them—the lab’s only decoration—hangs across the windows, a relic of a Día de Muertos party last fall.
Suarez’s contribution to the CMS upgrade is in the early stages. A series of concentric circles, drawn across a patchwork of plywood and paper on a workbench in the center of the room, represent the dimensions of the device—a minimum ionizing particles timing detector (MTD). The drawing will be replaced by sheet metal, which will then be covered by a dense grid of readout boards—green plastic rectangles covered with clusters of wires and chips. Designing the circuit boards is Suarez’ responsibility.
She picks up an assembled readout board that’s plugged into a computer for testing. The face of the detector will eventually be covered by 1,300 boards, each helping to translate a flood of information, collected by 29,000 silicon sensors, into digital data. Suarez points out a tiny terrier emblem with red LED eyes affixed to the plastic board, an homage to the device’s birth place in a BU lab.
The MTD, like everything at the Switzerland facility, involves many collaborators. The National Institute of Nuclear Physics in Turin, Italy, is working on the detector’s silicon sensors; Fermilab in Illinois is building circuit chips; MIT is working on detector mechanics; and the University of Nebraska–Lincoln is assembling the sensors and chips into detector modules. A miniature MTD, designed by Daniel Spitzbart, a postdoc in Suarez’ lab, will be replicated by each lab so they can test and optimize their components. Suarez and her team will work with peers at Rice University to produce the final readout boards, then the pieces will be shipped to CERN for installation in 2025.
The CMS helps scientists observe phenomena never seen before, like the creation of the Higgs boson, a particle that gives mass to the leptons and quarks that form the building blocks for matter. CERN scientists first observed the Higgs boson in 2012 and, as the CMS has been upgraded over time, have been able to study it in ever greater detail. The MTD will be part of the largest CMS upgrade yet, part of CERN’s preparations for high-luminosity collisions in the LHC that will begin in 2029.
Once in place, Suarez says, the MTD will provide 30 to 40 picoseconds in resolution (1 picosecond equals one trillionth of a second), a 25 percent improvement. Using the massive amounts of data collected by timing, trajectory, and energy detectors, scientists can recreate each particle collision to learn where a particle came from and how it behaved in its brief lifespan.
In 2021, Suarez received a five-year, $750,000 Early Career Award from the Department of Energy to fund her use of the CMS Detector and artificial intelligence to advance the study of dark matter and, in 2022, Astronomy magazine named her one of 25 rising stars. The MTD upgrades will help her search for “dark sector” particles. These previously unobserved particles are thought to be created by collisions in the LHC, but they quickly decay into known particles.
A Welcoming Place
Suarez speaks fondly of CERN. She enjoys seeing the distant Globe of Science and Innovation, CERN’s dramatic domed visitor center, as she approaches along the main road from Geneva. She likes exploring the streets, which are all named for scientists: Route Einstein running into Route Schrodinger, Route Marie Curie connected to Route Bohr. And then there’s the CMS itself.
“Our experiment is really beautiful—there’s turquoise cables, red cables,” she says. “Every time I go into the experimental cavern, it just makes me so happy.” It’s a space with which she’s developed an intimate familiarity, having been involved with the hardware and the data since her first visit in 2010. As a student, Suarez says, “I got to work on developing electronics and installing those electronics and seeing the first data events that were coming from them. That experience was an incredible experience.”
Though she always felt welcomed by the CERN community, she noticed that few of its members looked like her. “I have pictures of when I was a grad student and I was the only woman on the projects,” she says.
How she ended up there is an unlikely story. Suarez moved to the US from Mexico when she was 11 years old and had to learn English to catch up to her peers. A strong student in Mexico, Suarez felt stuck in her English as a second language classes—even petitioning the school, her mother claims, to move her into classes with English speakers. “It was kind of a traumatic experience, being in this new world,” she says. What helped Suarez navigate that period was a language that she already knew: math.
“Math was the one thing that was still the same,” she says. “That helped me get through some of those barriers. It gave me a lot of confidence, especially in my identity.”
Suarez was the first in her family to attend college and, she says, “I didn’t know anything about academia.” Then, through a community college physics class, she got the chance to spend a summer working in a University of California Santa Barbara lab. She had assumed she’d become a school teacher, but that summer changed her perspective. “I thought to myself, I never want to have a regular job again. I want to do research,” says Suarez, who went on to earn a BS in physics from UCLA and a PhD in physics from Texas A&M.
US Census Bureau data shows that the number of women in STEM jobs is on the rise—27 percent of STEM workers in the US are women, up from 8 percent in 1970—though that doesn’t reflect that women earn more than half of STEM degrees. According to the Pew Research Center, the numbers for Black (9 percent) and Hispanic (8 percent) STEM workers lag even further behind.
Suarez hopes to keep those numbers moving in a positive direction by exposing her students to the kinds of learning experiences she had. She takes them to CERN, where they can collaborate in the experiments with scientists from around the world. On the weekend, they go hiking in the nearby Alps. At BU, Suarez and her physics colleagues established a National Science Foundation-funded Research Experiences for Undergraduates (REU) program. Along with other Arts & Sciences departments, they utilize a holistic admissions process, recruit at national diversity in STEM conferences, and offer application fee waivers to help recruit diverse PhD applicants.
Those efforts have begun paying off. “Nearly 100 percent of our REU participants and 50 percent of admitted PhD candidates this year are from an underrepresented community,” Suarez says. And, more than a decade after she first visited CERN, “It’s nice to no longer be the only woman and person of color in the room.”