We report measurements by the T2K experiment of the parameters ${\theta }_{23}$ and $\mathrm{\Delta }{m}_{32}^2$ 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 $7.482\times 10^{20}$ POT in neutrino running mode and $7.471\times 10^{20}$ POT in antineutrino mode, T2K obtained ${\sin }^2({\theta }_{23})=0.51_{-0.07}^{+0.08}$ and $\mathrm{\Delta }{m}_{32}^2=2.53_{-0.13}^{+0.15}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ for neutrinos, and ${\sin }^2({\overline{\theta }}_{23})=0.42_{-0.07}^{+0.25}$ and ${\mathrm{\Delta }{\overline{m}}^2}_{32}=2.55_{-0.27}^{+0.33}\times {10}^{-3}{\mathrm{eV}}^2/{\mathrm{c}}^4$ 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.

• Received 25 April 2017

DOI:https://doi.org/10.1103/PhysRevD.96.011102

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Published by the American Physical Society