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

TL;DR

This paper reports the first measurement of muon neutrino charged current single positive pion production cross section on water at around 0.8 GeV using the T2K near detector, providing important data for neutrino interaction models.

Contribution

It presents the first differential cross section measurements of this process on water at T2K, with results compared to NEUT and GENIE predictions, highlighting model agreements and discrepancies.

Findings

Measured total cross section: 4.25 ± 0.48 (stat) ± 1.56 (syst) × 10^{-40} cm^2/nucleon.

Total cross section agrees with NEUT prediction, lower than GENIE prediction.

Differential distributions match NEUT well; GENIE overestimates overall normalization.

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 $p_{\pi^+}>200$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 $\langle\sigma\rangle_\phi=4.25\pm0.48 (\mathrm{stat})\pm1.56 (\mathrm{syst})\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$. The total cross section is consistent with the NEUT prediction ($5.03\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$) and 2$\sigma$ lower than the GENIE prediction ($7.68\times10^{-40} \mathrm{cm}^{2}/\mathrm{nucleon}$). 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.