We report a measurement of the flux-integrated νμ charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are
σ^{H2O}_{CC}=(0.840±0.010(stat.)+0.10−0.08(syst.))×10−38cm2/nucleon, σ^{CH}_{CC}=(0.817±0.007(stat.)+0.11−0.08(syst.))×10−38cm2/nucleon, and σ^{Fe}_CC=(0.859±0.003(stat.)+0.12−0.10(syst.))×10−38cm2/nucleon,
respectively, for a restricted phase space of induced muons: θμ<45∘ and pμ>0.4 GeV/c in the laboratory frame. The measured cross section ratios are σ^{H2O}_{CC}/σ^{CH}_CC=1.028±0.016(stat.)±0.053(syst.), σ^{Fe}_{CC}/σ^{H2O}_{CC}=1.023±0.012(stat.)±0.058(syst.), and σ^{Fe}_{CC}/σ^{CH}_{CC}=1.049±0.010(stat.)±0.043(syst.). These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses.
