Measurement of single charged pion production in the charged-current interactions of neutrinos in a 1.3 GeV wide band beam

Single charged pion production in charged-current muon neutrino interactions with carbon is studied using data collected in the K2K long-baseline neutrino experiment. The mean energy of the incident muon neutrinos is 1.3 GeV. The data used in this analysis are mainly from a fully active scintillator detector, SciBar. The cross section for single ${\pi }^{+}$ production in the resonance region ($W<2\mathrm{GeV}/c^2$) relative to the charged-current quasielastic cross section is found to be ${0.734}_{-0.153}^{+0.140}$. The energy-dependent cross section ratio is also measured. The results are consistent with a previous experiment and the prediction of our model.

Figure 1

The simulated neutrino energy spectrum for all muon neutrino interactions in the fiducial volume of the SciBar detector.

Figure 2

Schematic view of the near neutrino detector.

Figure 3

Diagram of SciBar.

Figure 4

The cross sections for charged-current single pion production calculated in NEUT compared to experimental measurements, ($•$) GGM [7],($▾$) ANL [12].

Figure 5

Number of vertex-matched tracks. Most events are 1-track, i.e. only the SciBar-MRD track. ${\chi }^2/\mathrm{d}.\mathrm{o}.\mathrm{f}=3.46/4$ considering the systematic errors discussed in Sec. 5.

Figure 6

$\Delta {\theta }_p$, angle between expected proton track assuming CCQE and the observed second track for the 2-track sample. ${\chi }^2/\mathrm{d}.\mathrm{o}.\mathrm{f}=32.58/30$ considering the systematic errors discussed in Sec. 5.

Figure 7

MIP confidence level for the second track in the 2-track nonQE sample in log scale. ${\chi }^2/\mathrm{d}.\mathrm{o}.\mathrm{f}=6.36/20$ considering the systematic errors discussed in Sec. 5.

Figure 8

Muon momentum distributions for each of the four data samples used in this analysis.

Figure 9

Muon angle distributions for each of the four data samples used in this analysis.

Figure 10

1-, 2-, and 3-sigma contours for parameters $R^{\mathrm{CC}1{\pi }^{+}}$ and $R^{\mathrm{other}\mathrm{nonQE}}$ for the energy-independent fit.

Figure 11

Comparison between the energy-dependent cross section ratio measurement and MC prediction. The vertical bars indicate the combination of the fit, nuclear, and other systematic uncertainties of the measurement.

Figure 12

Energy-dependent cross section ratio measurement compared to a previous result obtained by the ANL 12-foot bubble chamber experiment. ANL $\mathrm{CC}1{\pi }^{+}$ (with no hadronic invariant mass cut) and CCQE cross sections used in the comparison are taken from [12, 46], respectively. The vertical bars indicate the combination of the fit, nuclear, and other systematic uncertainties of the measurement.