Search for Electron Antineutrino Appearance in a Long-baseline Muon Antineutrino Beam

Understand

Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the PMNS mixing matrix.

• T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events.
• Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40{\sigma} and no discrepancy between data and PMNS predictions is found.
• A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.