First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector

Abstract

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies $\sim 0.8$ GeV. The differential measurements are presented as a function of muon and pion kinematics, in the restricted phase-space defined by $p_{\ddot{I}{€}^{+}}>200$MeV/c, $p_{\hat{I}{¼}^{-}}>200$MeV/c, $\cos \hat{I}{¸}_{\ddot{I}{€}^{+}}>0.3$ and $\cos \hat{I}{¸}_{\hat{I}{¼}^{-}}>0.3$. The total flux integrated $\hat{I}{½}_{\hat{I}}¼$ charged current single positive pion production cross section on water in the restricted phase-space is measured to be $⟨\ddot{I}ƒ{⟩}_{\ddot{I}}•=4.25\pm 0.48(\mathrm{stat})\pm 1.56(\mathrm{syst})\times 10^{-40}{\mathrm{cm}}^2/\mathrm{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times 10^{-40}{\mathrm{cm}}^2/\mathrm{nucleon}$) and 2$\ddot{I}ƒ$ lower than the GENIE prediction ($7.68\times 10^{-40}{\mathrm{cm}}^2/\mathrm{nucleon}$). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but over-estimates the overall cross section normalization.