Neutrinos have puzzled scientists for more than 50 years, and a recent study from physicists at William & Mary has shed new light into their mysterious behaviors.
Neutrino oscillation is a phenomenon of quantum mechanics where a neutrino’s lepton flavor changes as it moves. There are three possible flavors, and the probability of observing each one depends on its position throughout space.
There are three different flavors of neutrinos – muon, electron or tau. Scientists have long been captivated by the way they oscillate, because observing the change in flavor implies that neutrinos have a mass that isn’t zero.
Physicists have designed many experiments over time to test Bruno Pontecorvo’s prediction in 1957 that neutrinos would oscillate between lepton flavors. The solar neutrino oscillation experiment was one of the first, during which Ray Davis observed a difference in the number of solar neutrinos compared to the prediction of the Standard Solar Model. Researchers discovered that neutrinos oscillate inside of the sun, albeit through a different process than the vacuum oscillation observed in later experiments.
The Super Kamiokande experiment in 1998 provided one of the first precise measurements that confirmed neutrino oscillation when scientists noticed a deficit in the ratio of the flux of muon to electron neutrinos high up in the atmosphere.
Now, physicists at William & Mary have confirmed that neutrinos blasted through a 500-mile underground tunnel did, in fact, oscillate. Researchers at the Fermilab in Batavia, Illinois spent 10 years building an enormous particle detector to fire a beam of neutrinos along its length. The physicists observed a much higher incidence of muon-to-electron oscillations than they expected, confirming that the neutrinos changed flavors while they traveled.
The study’s results were presented at the American Physical Society’s Division of Particles and Fields conference in Ann Arbor, MI, and the researchers involved were “ecstatic” about their findings.