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

KEK. 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 $p_{\pi^+} > 200$ MeV/c, $p_{\mu^-} > 200$ MeV/c, $\cos\theta_{\pi^+} > 0.3$ and $\cos\theta_{\mu^-} > 0.3$. The total flux integrated $\nu_\mu$ charged current single positive pion production cross section on water in the restricted phase-space is measured to be $\langle\sigma\rangle_\phi=4.25\pm0.48~(\mathrm{stat})\pm1.56~(\mathrm{syst})\times10^{-40}~\mathrm{cm}^{2}/\mathrm{nucleon}$.

Data points taken from attached tar file available at http://t2k-experiment.org/results/.