The MINERvA collaboration analyzed data from the interactions of an antineutrino—the antimatter partner of a neutrino—with a nucleus. They were surprised to find evidence that antineutrinos interacted with pairs of particles inside the nucleus. They had expected antineutrinos to interact with just single protons or neutrons. To see this evidence, the team compared their antineutrino data to a model of these interactions. The model was based on a previous analysis of neutrino interactions at MINERvA published two years ago.