At an event marking a major step forward for particle physics, construction has begun on the Deep Underground Neutrino Experiment (DUNE), a multibillion-dollar facility located a mile beneath the former Homestake gold mine in Lead, South Dakota. This ambitious project will study neutrinos, the least understood particle in the Standard Model, by detecting beams originating in Illinois; the experiment relies on an international collaboration involving 38 countries and contributions from CERN, including 10 million pounds of steel for the first vessel. “As a South Dakotan, knowing that on this ground, our little piece of the planet, we are going to transform our understanding of matter is pretty incredible,” said Representative Dusty Johnson of South Dakota. DUNE aims to unravel the mysteries surrounding these elusive particles, potentially revealing why matter exists at all, and represents over two decades of work for the physics community.
Deep Underground Neutrino Experiment: Facility and Scale
A multibillion-dollar investment is currently reshaping a former gold mine into a particle physics facility. This isn’t simply a new laboratory; it’s a transformation of the historic Homestake gold mine, repurposed for the pursuit of fundamental physics. The scale of DUNE extends far beyond the South Dakota location. Physicists will utilize a particle accelerator at Fermilab in Batavia, Illinois, to generate the most intense neutrino beam ever created, officially known as the Long-Baseline Neutrino Facility (LBNF). This beam will be directed westward, traveling 800 miles to intersect with the cavernous detectors being built at the Sanford Underground Research Facility. “Everything about DUNE is large: the most intense neutrino beam, the biggest liquid argon detectors, the longest distance neutrinos will travel,” says Sowjanya Gollapinni, co-spokesperson of the DUNE collaboration.
The experiment relies on this long-distance connection, sending particles from one state to be detected in another, highlighting the collaborative and complex logistical demands of the research. Construction began with the signing of the first steel beam destined for underground installation, a symbolic act marking the start of building the detectors. The initial phase involves installing 10 million pounds of steel for the first vessel through a 20-foot-wide shaft, covering only the first of two massive containers designed to hold liquid argon. Project leaders describe the process as akin to “building a ship inside a glass bottle—except the neck of the bottle is a mile long, and the ship is a one-tenth-scale aircraft carrier.” Maintaining the argon in a liquid state requires extreme cold, just a few degrees above -300 degrees Fahrenheit, and the containers will ultimately be laced with intricate wire grids, painstakingly hand-strung.
Despite accruing approximately five years of delay, the current goal is to have the first detector operational by early, with initial results regarding neutrino mass ordering potentially arriving at a later date. Gollapinni adds, “DUNE has been the dream of many in the physics community for more than two decades; it’s the moment when this becomes real.” The project’s total cost has reached nearly $5 billion, a significant investment reflecting the ambition and potential impact of the experiment on our understanding of the universe.
Fermilab’s Long-Baseline Neutrino Facility Beam Production
At Fermilab in Batavia, preparations are well underway to upgrade existing accelerator technology to produce a neutrino beam far exceeding any previously created; this is a substantial leap in capability. This beam production isn’t a standalone operation, but is intrinsically linked to the massive detector being constructed within the repurposed Homestake gold mine. The beam will be directed downward and westward, traveling through the Earth to intersect with the detector’s core, a cavernous space carved out of the former mine. This steel, now beginning its journey underground through a 20-foot-wide shaft, represents the first physical step in assembling the apparatus that will capture these elusive particles. While the project has faced delays, accumulating roughly five years, and its total cost has risen to nearly $5 billion, the ambition remains unwavering.
It’s very important for this experiment itself, but I think it’s very important for the future of particle physics in the U.S., too.
Edward Blucher, a DUNE physicist at the University of Chicago
Neutrino Oscillation and the Standard Model’s Mysteries
Beyond simply detecting these elusive particles, DUNE is designed to address fundamental gaps in the Standard Model of particle physics, specifically the perplexing phenomenon of neutrino oscillation and its potential link to the imbalance between matter and antimatter in the universe. Scientists have long observed that neutrinos change “flavor” as they travel, morphing between types, a behavior not predicted by the original Standard Model, and DUNE’s scale is intended to precisely measure these transformations. The experiment’s approach builds upon decades of neutrino research, where beams of these particles are generated at sources like particle colliders and directed towards distant detectors to measure flavor changes in transit. This beam will travel 800 miles westward, terminating at the heart of DUNE’s cavernous detector, filled with tens of millions of pounds of liquid argon kept at a frigid -300 degrees Fahrenheit.
The jostling argon atoms will release detectable electrons when struck by the rare passing neutrinos, providing data on their interactions and oscillations. The connection between neutrino behavior and the matter-antimatter asymmetry is a central mystery. The Standard Model predicts equal creation of both matter and antimatter, yet the observable universe is overwhelmingly dominated by matter. Physicists theorize that the unique properties of neutrinos, specifically their shape-shifting, may hold the key to understanding this imbalance. “Why is there something rather than nothing?” is the almost philosophical question DUNE hopes to address, by precisely measuring neutrino masses and interactions. However, DUNE is not operating in isolation; Japan’s Hyper-Kamiokande and China’s Jiangmen Underground Neutrino Observatory are also pursuing similar research, with JUNO providing results late last year. Edward Blucher, a DUNE physicist at the University of Chicago, acknowledges the collaborative nature of the field, stating, “In 20 years, we’re going to know much more about this kind of science, and it’s going to be a result of things that were measured with Hyper-K and JUNO and DUNE.”
In 20 years, we’re going to know much more about this kind of science, and it’s going to be a result of things that were measured with Hyper-K and JUNO and DUNE.
Edward Blucher, a DUNE physicist at the University of Chicago
International Competition: Hyper-K and JUNO Experiments
The pursuit of understanding neutrinos isn’t solely a U.S. endeavor; international competition is rapidly intensifying alongside the ambitious Deep Underground Neutrino Experiment (DUNE). While DUNE, with its multibillion-dollar price tag, nearly $5 billion, represents the largest particle physics project undertaken in the United States, both Japan and China have launched complementary experiments poised to contribute significantly to the field, and potentially surpass aspects of the American program. These parallel efforts highlight the global nature of fundamental physics research and the urgency to resolve long-standing mysteries surrounding these elusive particles. Japan’s Hyper-Kamiokande (Hyper-K) is currently on track to start taking data, potentially allowing it to measure the matter-antimatter asymmetry before DUNE is fully operational. This timeline creates a competitive dynamic, as Hyper-K’s more modest approach may still yield crucial insights.
Meanwhile, China’s Jiangmen Underground Neutrino Observatory (JUNO) has already begun delivering results, having released its first data late last year. “JUNO is essentially a downscaled and entirely independent version of DUNE,” offering a valuable cross-check on findings and potentially accelerating the pace of discovery. Despite the significant investment and five-year delays already accrued by DUNE, project leaders remain focused on successful execution. “All of us are acutely aware that a huge investment has been made in this project and that we have to execute it successfully,” Blucher concludes, adding that the experiment’s success is “very important for the future of particle physics in the U.S., too.” The race to unravel the secrets of neutrinos is therefore not a zero-sum game, but rather a multifaceted global effort with the potential to reshape our understanding of the universe and the very nature of matter.
DUNE has been the dream of many in the physics community for more than two decades.
Sowjanya Gollapinni, co-spokesperson of the DUNE collaboration
