Updated T2K measurements of muon neutrino and antineutrino disappearance using 1.5 × 10²¹ protons on target

We report measurements by the T2K experiment of the parameters θ23 and ∆m²₃₂ 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 × 10²⁰ POT in neutrino running mode and 7.471 × 10²⁰ POT in antineutrino mode, T2K obtained, sin²(θ23) = 0.51⁺⁰₋₀^._.⁰⁸₀₇ and ∆m²₃₂ = 2.53⁺⁰₋₀^._.¹⁵₁₃ × 10⁻³eV²/c⁴ for neutrinos, and sin²(θ23) = 0.42⁺⁰₋₀^._.²⁵₀₇ and ∆m²32 = 2.55⁺⁰₋₀^._.³³₂₇ × 10⁻³eV²/c⁴ 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.