January 26, 2021
The COHERENT particle physics experiment at the Department of Energy’s Oak Ridge National Laboratory has firmly established the existence of a new kind of neutrino interaction. Because neutrinos are electrically neutral and interact only weakly with matter, the quest to observe this interaction drove advances in detector technology and has added new information to theories aiming to explain mysteries of the cosmos.
“The neutrino is thought to be at the heart of many open questions about the nature of the universe,” said Indiana University physics professor Rex Tayloe. He led the installation, operation and data analysis of a cryogenic liquid argon detector for neutrinos at the Spallation Neutron Source, or SNS, a DOE Office of Science User Facility at ORNL.
The study, published in Physical Review Letters, observed that low-energy neutrinos interact with an argon nucleus through the weak nuclear force in a process called coherent elastic neutrino-nucleus scattering, or CEvNS, which is pronounced “sevens.” Like a ping-pong ball bombarding a softball, a neutrino that hits a nucleus transfers only a small amount of energy to the much larger nucleus, which recoils almost imperceptibly in response to the tiny assault.
Laying the groundwork for the discovery made with the argon nucleus was a 2017 study published in Science in which COHERENT collaborators used the world’s smallest neutrino detector to provide the first evidence of the CEvNS process as neutrinos interacted with larger and heavier cesium and iodine nuclei. Their recoils were even tinier, like bowling balls reacting to ping-pong balls.
Read more at ornl.gov/news.
Related Publication: Akimov, D. et. al. (2021) First Measurement of Coherent Elastic Neutrino-Nucleus Scattering on Argon. Physical Review Letters, 126, 012002. doi.org/10.1103/PhysRevLett.126.012002