CONSEQUENCES. “The probability of this oscillation occurring is small, but it holds the key to leptonic CP violation: if CP symmetry is conserved, the oscillation probability for muon-to-electron neutrino conversion would be the same as that for muon-to-electron antineutrino conversion.” (CP = charge-conjugation parity-reversal).
https://www.nature.com/articles/d41586-020-01000-9