This Handheld Detector Spotted A Never-Before-Seen Physics Phenomenon
A collaboration has detected neutrino particles bouncing off of atomic nuclei, a never-before-seen phenomena, using a detector so small it could be transported by hand and adopted to functions like nuclear weapon detection.
The Wallflower Particle
It sounds like the setup to a nerdy joke: “What did the physicists say when they saw a neutrino bump into a nucleus? Finally!”
In a study, published August 3rd in Science, researchers from the Oak Ridge National Laboratory (ORNL) and UChicago announced that they had observed phenomena that have eluded physicists for decades: elusive neutrino particles bouncing off of a nucleus.
Neutrinos have long been difficult to spot, due to their famously shy nature. Unlike most elemental particles, they rarely interact with other particles. So, when physicist Daniel Freedman proposed in 1974 that they might bump off of atomic nuclei, a phenomenon known as coherent elastic neutrino-nucleus scattering (CEvNS), he wrote that “our suggestion may be an act of hubris” because of how difficult experimental confirmation would be.
“Why did it take 43 years to observe this interaction?” asked Juan Collar, co-author of the Science study and a professor of physics at UChicago, in a press release. “What takes place is very subtle.”
Previous searches for neutrinos have tackled the problem by throwing as many particles at them as possible, using enormous tanks built underground.
In contrast, the ORNL collaboration — known as COHERENT — utilized a new type of detector about the size of a fire extinguisher, which searched specifically for the fingerprint of CEvNS. When a neutrino collides with a nucleus, the nucleus recoils slightly from the impact, and displaces a few electrons from their orbits around the nucleus and its neighboring particles in the process.