We report measurements by the T2K experiment of the parameters θ23
and Δm322 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)=0.51−0.07+0.08 and Δm322=2.53−0.13+0.15×10−3eV2/c4 for neutrinos, and
sin2(θ23)=0.42−0.07+0.25 and
Δm232=2.55−0.27+0.33×10−3eV2/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.Comment: 8 pages, 2 figure