Challenging the Standard Model
April 28, 2023
Assistant Professor Lawrence Lee has won $1 million from the National Science Foundation through the Early Career Development (CAREER) Program, an initiative offering the foundation's most prestigious awards in support of young faculty members.
Lee's work pushes past what we know about the elementary particles that make up all matter (asteroids and baseballs and carbon atoms) to see what else is there. He's keen to share what he learns with science fans and non-science fans alike, be that on the dance floor (really) or through exhibitions designed by art students. Research and outreach are two halves of an important whole framing Lee's proposal: growing a strong talent pool in science, technology, engineering, and math (STEM). With appreciation for what's already been done and enthusiasm to see what comes next, his NSF-sponsored work aims to inspire a new generation of physicists and science-supporting citizens.
Lee joined the physics department in 2021 as a particle physicist looking to break out of scientific confinements, both theoretical and practical. His curiosity compels him to travel beyond the rather tidy borders of the Standard Model to look for new particles, and consequently new physics. To do so he'll upgrade a wildly successful detection system designed when he was in elementary school.
Lee is part of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) in Geneva, Switzerland. The LHC can be thought of as a 27-kilometer racetrack where scientists intentionally create subatomic head-on collisions. They accelerate two beams of particles and smash them together at four different spots, each with a particle detector to see what results from the impact. CMS is one of those detectors. Particles quickly emerge after the crash, allowing the detector to identify them and measure their momenta and energy. Lee sees potential for the detector to look outside the framework of known particles to find new ones.
"We usually assume that the particles leaving signals in our detector are those from the Standard Model," he said. "Many theory models for physics beyond the Standard Model predict the existence of heavy new particles that can travel into the detector, and have unexpectedly large interactions."
But why not just stick with this model that's done so much to sort out particles and forces and help us understand how magnets work and what powers our Sun? What's left to know? Plenty, it turns out.
"The Standard Model is a nice little story that has led to some of the most successful predictions in science, ever," Lee said. "But it can't be the whole picture. It's wild for us to believe that our little model from 50 years ago, that describes today's lab conditions on Earth, is all there is in the universe."
Obvious omissions he pointed to are "the gravity we know and love or huge amounts of dark matter that seem to be there when we look at the sky.
"Science is about finding answers," he said. "The Standard Model leaves us with so many questions, so we're going to keep digging."
New particles, then, can help us expand the sliver of the universe we've begun to understand. But how to detect them?
"My group is working on using low-level detector information to distinguish these new heavy particles from Standard Model particles," Lee said. "We can carefully sift through the data that we have today and that we'll collect in the next few years to try and find something incompatible with the Standard Model."
A key to making this work is upgrading the CMS detector, which underwent the first phase of construction in 1998 and took its first measurements in 2009. The CMS experiment has had starring roles in physics breakthroughs including discovery of the Higgs boson. New science, however, will require a bit of freshening up. A revamped CMS will go hand-in-hand with the LHC's forthcoming High-Luminosity project, as higher luminosity translates into more data for detectors to gather. This means there will be many more particle "footprints" to follow.
"We're upgrading the CMS detector in ways that will give it new capabilities, particularly in the initial filtering of collision events," Lee explained. "We're going to provide much more information about charged particles to this filtering stage (the 'trigger') such that we can continue to probe these anomalous tracks with new tools."
Of note in Lee's proposal is a plan for upgrading the CMS detector so it can collect data for years to come without considerable reworking.
"We are always subject to the decisions of the past, especially for these long time-scale projects," he explained. "The overall structure of CMS was designed decades ago. My program has been all about trying to use the system we have creatively to get additional physics sensitivity for signatures that the experiment was not designed for."
This, he said, takes a lot of work, a lot of deep understanding, and a lot of creativity.
"For the future," he continued, "we have various opportunities to try and create an upgraded detector that is as inclusive as possible for potential new physics signatures. We're not going to get it perfect, but we can push to not over-optimize for a particular signature and preclude out-of-the-box thinking."
For Lee, a central theme of good research is accepting that over centuries of modern science all claims of complete knowledge ultimately collapse.
"There are always surprises around the corner when we continue to explore the unknown," he said. "The Standard Model has held up strong so far, so we need to start challenging it in more specific and less orthodox ways, and this is my research program. Eventually the (model) will fail, and when that happens, we'll be there to help tear it down and figure out what replaces it."
Lee is well aware that not everyone shares his enthusiasm for subatomic particles or massive detectors. He's not at all insulted by that. When he's talking to colleagues, he knows he's preaching to the choir. And he knows that science outreach programs are often aimed at people who are at least interested enough to show up for a Saturday morning lecture. He calls that "preaching to the congregation." As with his research, Lee's NSF-sponsored outreach goes beyond the confines of what's been done.
The first of two components is ColliderScope, a mix of repurposed lab equipment and funk where Lee creates audio waveforms to paint musical pictures. At music festivals all over the world he's gotten people to the dance floor who had no idea they were rocking out to particle physics. (He won the College of Arts and Sciences Outreach Teaching Award for the project.) He plans to expand his schedule and offer more shows, focusing on a U.S. audience. He's also adding an experimental cloud chamber element, so while the music gets people moving, they'll also learn about the cosmic rays moving through them.
"(Cosmic rays) are a beautiful playground of particle physics, relativity, astronomy, cosmology, etc.," Lee explained. "And they're not only in a lab. It's incredibly democratic in that every one of us has a huge number of cosmic rays passing through our bodies at all times. What better way to connect the public to our particle physics research than to show them that particle physics is all around (and through!) us."
Lee will expand on this notion to develop CosmoVision. He and Professor David Matthews from UT's School of Interior Architecture will create a senior-level design course where UT students use cloud chambers to build a transportable educational exhibit.
"The over-arching goal of the CosmoVision project is to connect the normally invisible cosmic rays to something that you can experience with your own senses such that the public can really 'feel' and intuit," Lee said.
He and Matthews are actually neighbors who've collaborated in the past to build a school outreach exhibit on the physics of sound. This encore project will give design students an opportunity to brainstorm what the CosmoVision experience will be and see that vision through to a finished product to engage general audiences and school groups.
"Integrating STEM education into the artistic design process is the most serious realization of the STEAM (science, technology, engineering, arts and mathematics) ideal that I can imagine," Lee said. "I can't wait to see what we can come up with together as a team."
Lee hopes this outreach plan will recruit future scientists and also share a fun side of physics with people who'll never set foot in a lab.
"I'm interested in having a robust pipeline of STEM-education directly within my group," he said. "I want significant training to happen from the undergraduate level all the way through the academic ranks, including with myself."
His expectation of all scientists—including those he mentors—is that they engage with everyone, even if that means taking the show on the road.
"I want everyone to seriously participate in outreach and educational activities — yes, to grade school students, but also to the government, the general public that loves science, and most importantly the general public that does not particularly love science," he said.
"Most taxpayers — most of the people who are funding our work — don't seek out a physics lecture in their free time," he continued. "A major goal of my programs is to connect with a different slice of the population, focusing on experiences, culture, and art that anybody can connect with, to make new enthusiastic supporters of basic research today."
Lee's award officially begins June 1 and includes five years of NSF support. This makes eight NSF CAREER Awards for UT Physics since 2012:
- Larry Lee (2023)
- Steve Johnston and Jian Liu (2019)
- Lucas Platter and Andrew W. Steiner (2016)
- Haidong Zhou (2014)
- Jaan Mannik (2013)
- Norman Mannella (2012)
Learn more about the CMS Experiment Group at UT.