T2K scientists are tracking a curious property of neutrinos, hard-to-detect particles that rarely interact with matter. Neutrinos change type, or flavor, as they travel — for example, muon neutrinos might turn into electron neutrinos.
The T2K experiment has been watching how both regular neutrinos and antineutrinos oscillate between flavors, and they’ve noticed there’s a slight disparity in how they behave.
The transition of a muon neutrino to an electron neutrino happens at a higher rate than that of a muon antineutrino to an electron antineutrino, says Mark Hartz, a particle physicist at Canada’s York University and co-author of a recent Nature paper on the T2K data. The data provide further evidence that there could be some slight asymmetries between normal matter and antimatter, perhaps enough to explain why the universe today is almost exclusively made of matter.
But Nobel laureate Samuel Ting, the principal investigator of the AMS experiment, says we need more data to truly say antimatter isn’t out there somewhere.
“This neutrino experiment only says, ‘From Earth, we observe in space more matter than antimatter,’ ” he says. “It does not say, ‘Antimatter disappeared.’ ”
Ting’s views may not represent the majority opinion among scientists, but the physicist is undaunted: “If you don’t look, then really you will never know.”
This article appeared in the June 2021 issue of Discover
magazine as "The Search Goes On."