When a star reaches the end of its life, it cools off, collapses in on itself, and explodes in a spectacular show of light that can be seen across the universe.
“What we learn from this experiment will be groundbreaking, and that will be applied to everything from national security to astrophysics.”
Although these supernovae events are phenomenal, they are also quite rare. Prior to a supernova event in 2020, the most recent supernova in the Milky Way was more than 300 years ago.
Scientists look to supernovae for greater understanding of another, much more massive explosion—the Big Bang—a one-time event that created the universe. Studying the former could offer insights into a fundamental question in physics: Why does our universe exist at all? The creation of the universe actually goes against what modern physics would predict, and it comes down to post‑explosion particles.
Most of the energy from supernovae transforms into particle pairs consisting of neutrinos and anti-neutrinos. With equal mass but opposite charge, these particles annihilate—returning to pure energy—when they come back together. There is a mathematical balance, or so it’s thought. The existence of the universe (which is made of matter) boldly contradicts this idea of balance because it couldn’t exist unless the particles were in unequal quantities. Clearly, something doesn’t add up, and scientists around the world want to know why.
Researchers from 30 countries, including physicists from Los Alamos, have come together to solve this matter-antimatter paradox through a new experiment—the Deep Underground Neutrino Experiment, or DUNE. The plan is for DUNE to detect neutrino and anti-neutrino particles, which are challenging to find in abundant quantities in nature. Although DUNE is equipped to detect these particles via a supernova event (which acts as a surrogate for the Big Bang), the researchers opted to design DUNE with its own particle-generating beam. This is because supernovae are rare, occurring once in a galaxy only every century or so, and because the energy from supernova signals pales in comparison to what the accelerator beam can consistently produce. This frees the experiment from having to rely on a once-in-one-hundred-years supernova event, but if one does occur close by, DUNE will detect it.
Looking at the quantity and behavior of these particles will likely transform our understanding of physics.
“Neutrinos are peculiar particles that oscillate between three types, or flavors: electron, muon, and tau,” says Los Alamos physicist Sowjanya Gollapinni. “DUNE will help us compare the neutrino (matter) oscillation behavior to that of anti-neutrinos (antimatter).”
If the behavior is different, it could help explain why energy from the Big Bang converted into matter (i.e., a universe) and not antimatter.
DUNE is composed of a near-detector located underground at the Fermi National Accelerator campus in Illinois and a far‑detector located 800 miles away, deep underground at the Sanford Underground Research Facility in South Dakota. The particle‑generating beam, produced in Illinois, travels underground to South Dakota. “The DUNE far-detector will be the largest cryogenic detector ever to be built, containing 70,000 tons of liquid argon as target material for neutrinos to interact with,” Gollapinni says. The neutrino and anti-neutrino oscillations will be analyzed before and after their approximately 4-millisecond trip between detectors.
“Designing these state-of-the-art detectors was a significant accomplishment,” Gollapinni says. “What we learn from this experiment will be groundbreaking, and that will be applied to everything from national security to astrophysics.”
Next-generation neutrino experiments such as DUNE can provide valuable inputs to nuclear security applications, especially in the context of anti-neutrino detection and characterization. Developing such detection technology for monitoring nuclear reactors from distances of tens of kilometers away is ongoing, with the potential to improve safety.
Officially, ground has already been broken on the DUNE project. Excavation of the far-detector main cavern is underway, but detector installation isn’t expected until 2024. DUNE’s design and construction are massive undertakings, but the result holds the potential to unravel the mysteries of the universe.