From The New York Times, April 15, 2020: An international team of 500 physicists from 12 countries, known as the T2K collaboration, reported that they had measured a slight but telling difference between neutrinos and their opposites, antineutrinos. Fermilab Deputy Director Joe Lykken comments on the result and how the international Deep Underground Neutrino Experiment, hosted by Fermilab, may be able to make a definitive discovery of CP violation.

Fermilab’s NOvA neutrino experiment records in its giant particle detector the passage of slippery particles called neutrinos and their antimatter counterparts, antineutrinos. Famously elusive, these particles’ interactions are challenging to capture, requiring the steady accumulation of interaction data to be able to pin down their characteristics. With five years’ worth of data, NOvA is adding to scientists’ understanding of neutrinos’ mass and oscillation behavior.

The observation occurred just two hours after the lab’s accelerator complex switched to antineutrino delivery mode.

MINERvA measures the total probability that a muon neutrino (or antineutrino) interacts with the protons and neutrons inside the MINERvA detector via charged-current interaction.

The observation of the appearance of an electron neutrino proves conclusively that the NOvA experiment can measure electron neutrino appearance and confirms oscillations at greater than 3 sigma with primary analysis or 5 sigma with secondary analysis.