Fermilab Scientists Observe Neutrino Oscillations
Scientists working on the NOvA experiment at Fermilab have observed their first evidence of neutrino oscillations. The experimental results were released at the American Physical Society’s Division of Particles and Fields conference in Ann Arbor.
Neutrinos are elusive particles that interact only very weakly with ordinary matter. Neutrinos come in three types: muon neutrinos, electron neutrinos and tau neutrinos. Neutrinos oscillate, which means that they change from one type to another. One of the objectives of the NOvA experiment is the observation of oscillations from muon neutrinos to electron neutrinos.
Important Implications in Physics and Cosmology
In the experiment, neutrinos generated at Fermilab near Chicago travel more than 500 miles straight through the Earth to a far detector at Ash River, Minnesota (shown in the picture), oscillating along the way. Trillions of neutrinos are sent every second, but neutrino interactions are so weak that only a few neutrinos are observed and typed at the Minnesota detector.
The beam originating at Fermilab is made almost entirely of muon neutrinos. The data collected at the Minnesota detector indicate the presence of electron neutrinos.
“If oscillations did not occur, experimenters predicted they would see 201 muon neutrinos arrive at the NOvA far detector in the data collected; instead, they saw a mere 33, proof that the muon neutrinos were disappearing as they transformed into the two other flavors,” says the NOvA press release. “Similarly, if oscillations did not occur, scientists expected to see only one electron neutrino appearance (due to background interactions).”
But the collaboration saw six such events, evidence that some of the missing muon neutrinos had turned into electron neutrinos.
“People are ecstatic to see our first observation of neutrino oscillations,” said NOvA co-spokesperson Peter Shanahan of the U.S. Department of Energy’s Fermi National Accelerator Laboratory. “For all the people who worked over the course of a decade on the designing, building, commissioning and operating this experiment, it’s beyond gratifying.”
Besides studying neutrino oscillations, the NOvA experiment wants to study the neutrino masses. Neutrinos are about a million times lighter than the masses of other particles in the Standard Model of physics, but the masses of the three types of neutrinos are unknown. The Higgs Boson plays an important role in theoretical models of particle masses, but it isn’t clear if the same theoretical models can be applied to neutrinos. The third objective of the NOvA experiment is to study possible differences between neutrino and anti-neutrino oscillations, which would have deep implications in cosmology.
Understanding neutrino physics is very important in physics and cosmology, which fully justifies the cost of the NOvA experiment. It’s too early to think of using neutrinos for operational communications, but researchers from Fermilab and other laboratories have demonstrated low-rate communications using neutrinos in 2012, and scientists have speculated about the possibility to use neutrinos for SETI.
Images from Fermilab.