Measurement of Muon Neutrino Disappearance with the T2K Experiment

We describe the measurement of muon neutrino disappearance due to

neutrino oscillation using the Tokai-2-Kamiokande (T2K) experiment's Run 1-4 (6.57×1020 POT)

data set. We analyze the data using the conventional

Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing

matrix for the three Standard Model neutrinos. The output of the

analysis is a measurement of the parameters sin2θ₂₃, Δm2₃₂ for the normal hierarchy and sin2θ₂₃, Δm2₁₃ for

the inverted hierarchy. The best-fit oscillation

parameters for the normal hierarchy are found to be

(sin2θ₂₃, Δm2₃₂) = ( 0.514, 2.51×10-3 eV2/c4}). The 90% 1D confidence interval -- determined for both parameters

using the Feldman-Cousins procedure -- is for the normal hierarchy

0.428 < sin2θ₂₃ < 0.598 and

2.34×10-3 eV2/c4 < Δm2₃₂ < 2.68\times10^{-3} eV2/c4.

For the inverted hierarchy, the best-fit oscillation parameters are

(sin2θ₂₃, Δm2₁₃) = (0.511, 2.48×10-3 eV2/c4. The 90\% 1D Feldman-Cousins confidence intervals for the inverted hierarchy are 2.31×10-3 eV2/c4 < \Delta m^2_{13} < 2.64×10-3 eV2/c4.