Search for C P Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2 ×1021 Protons on Target
The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of 14.7 (7.6 )×1020 protons on target in the neutrino (antineutrino) mode, 89 νe candidates and seven anti-νe candidates are observed, while 67.5 and 9.0 are expected for δC P=0 and normal mass ordering. The obtained 2 σ confidence interval for the C P -violating phase, δC P, does not include the C P -conserving cases (δC P=0 , π ). The best-fit values of other parameters are sin2θ23=0.52 6-0.036+0.032 and ∆ m322=2.463-0.070+0.071×10-3 eV2/c4 .