Updated T2K measurements of muon neutrino and antineutrino disappearance using 1.5 x 10(21) protons on target

We report measurements by the T2K experiment of the parameters θ 23 and Δ m 2 32 governing the disappearance of muon neutrinos and antineutrinos in the three-flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using 7.482 × 1 0 20 POT in neutrino running mode and 7.471 × 1 0 20 POT in antineutrino mode, T2K obtained sin 2 ( θ 23 ) = 0.5 1 + 0.08 − 0.07 and Δ m 2 32 = 2.5 3 + 0.15 − 0.13 × 10 − 3 eV 2 / c 4 for neutrinos, and sin 2 ( ¯ θ 23 ) = 0.4 2 + 0.25 − 0.07 and Δ ¯ m 2 32 = 2.5 5 + 0.33 − 0.27 × 10 − 3 eV 2 / c 4 for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.