Hints of a ghosty, “sterile” version of the neutrino:
There are three types of neutrinos in the Standard Model, the blueprint of particle physics. But in past experiments, scientists have thought there could be a fourth, more mysterious type. Results from an experiment called MiniBooNE, combined with data from another called the Liquid Scintillator Neutrino Detector, seem to add even further evidence for the existence of the sterile neutrino.
Neutrinos are perhaps the second most common particle in the universe, after light particles, called photons. Physicists have long known about the electron neutrino, the muon neutrino, and the tau neutrino. They’ve also known that the neutrinos can swap identities, or oscillate, between types. And experiments seemed to observe neutrinos disappearing and reappearing, as if they’d swapped into a fourth, more difficult-to-observe identity….’