Unseen Oscillations

On Brookhaven Bits & Bytes, Steve Kettell brings us up to speed on a new research project taking place beneath a mountain in southern China. The object of study is the neutrino, which can “pass through the Earth and through much of the universe without interacting with anything.” Ethan Siegel explains on Starts With a Bang: “Neutrinos only interact gravitationally and through the weak force. They have no electromagnetic interactions.” And because they have no charge, neutrinos are free to pass between the atoms that make up tangible matter. Steve writes that neutrinos from the sun were first detected in the 1960s—but “only one third of the expected number was observed.” With the new detectors at Daya Bay, scientists can compare the number of neutrinos produced by nuclear reactors with the number detected almost two kilometers down the road. The neutrinos lost in between “would indicate that some of our electron antineutrinos had oscillated into tau antineutrinos, which we cannot physically observe.” Such a result would indicate another source of CP violation in nature and increase our understanding of particle physics.