![]() That interaction is called coherent elastic neutrino-nucleus scattering.īecause most nuclei are much bigger than individual protons or neutrons, scientists should see this type of interaction more frequently than interactions driven by higher energy neutrinos. As the nucleus receives the Z boson, the nucleus recoils slightly. As the neutrino releases the Z boson, the neutrino bounces away. Theorists proposed that when a low-energy neutrino approaches a nucleus, the two particles exchange an elementary particle called a Z boson. But if a neutrino's energy is low enough, it should interact with an entire nucleus rather than its individual parts. Most neutrinos only interact with individual protons and neutrons. While physicists had predicted this interaction more than 40 years ago, they had never detected it. Searching for a Coherent Answer with COHERENTĪ team of scientists from ORNL, other DOE national laboratories, and universities designed the COHERENT experiment to identify a specific interaction between neutrinos and nuclei. "Neutrinos may hold the clue to discovering particle physics beyond the Standard Model," said Karsten Heeger, a Yale University professor and co-spokesperson for PROSPECT. That would make them nearly impossible to detect.īut that's a big "if." A sterile neutrino would be the first particle not predicted by the Standard Model, physicists' summary of how the universe functions. Physicists theorize that if sterile neutrinos exist, they would interact with other particles even less than regular ones do. Some scientists have proposed a not-yet-seen particle called the sterile neutrino. In addition, they change type as they travel. There are three different types of neutrinos, each of which behaves differently. "There's no other way to answer a lot of the questions that we find ourselves having." Understanding how neutrinos interact may even help us understand why matter - and everything made out of it - exists at all.īut neutrinos haven't made answering these questions easy. "Neutrinos tell us a tremendous amount about how the universe is created and held together," said Nathaniel Bowden, a scientist at DOE's Lawrence Livermore National Laboratory and co-spokesperson for PROSPECT. While neutrinos are some of the smallest particles in the universe, investigating them may reveal massive insights. These two modest experiments supported by DOE's Office of Science are poised to fill some major gaps in our understanding of this strange particle. In fact, it's the smallest working neutrino detector in the world.īut COHERENT and a sister experiment at ORNL, PROSPECT, are showing that neutrino experiments don't have to be enormous to make big discoveries. Besides its mundane location, COHERENT's main detector is barely bigger than a milk jug. One is located at the South Pole, while another shoots neutrino beams hundreds of miles to a far detector. To catch a glimpse of these miniscule particles, most experiments use incredibly large machines, often in remote locations. The experiment, called COHERENT, poses a stark contrast to most other neutrino experiments. The basement location would protect the machines from exposure to background particles. Once scientists installed the experiment's detectors, they nicknamed the hallway "Neutrino Alley." After moving some water barrels to the side and conducting background tests, they were in business. "We were really fortunate to go into the basement one day," said David Dean, ORNL's Physics Division Director. But putting the neutrino detectors on the same floor as the SNS would expose the devices to background particles that would increase uncertainties. The SNS also produces neutrinos, which fly off in all directions from the particle accelerator's target. The neutrons the SNS produces drive 18 different instruments that surround the SNS like spokes on a wheel. Needless to say, they're notoriously difficult to detect.Īt first, the team surveyed a bustling area near the Spallation Neutron Source (SNS), a DOE Office of Science user facility at ORNL in Tennessee. In fact, trillions pass through the Earth every second, leaving no impression. They interact very little with other particles. The most abundant particles in the universe, neutrinos are extremely light and have no electric charge. The team uses five particle detectors to identify a specific interaction between neutrinos and atomic nuclei. But a tucked-away location in the recesses of the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) provided exactly what Yuri Efremenko was looking for.Įfremenko, an ORNL researcher and University of Tennessee at Knoxville professor, is the spokesperson for the COHERENT experiment, which is studying neutrinos. Except in horror movies, most scientific experiments don't start with scientists snooping around narrow, deserted hallways.
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