Measurement of the ${\nu }_{\mu }$ charged current quasielastic cross section on carbon with the T2K on-axis neutrino beam

We report a measurement of the ${\nu }_{\mu }$ charged current quasielastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasielastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are $(11.95\pm 0.19(\text{stat}{)}_{-1.47}^{+1.82}(\text{syst}))\times 10^{-39}{\mathrm{cm}}^2/\text{neutron}$, and $(10.64\pm 0.37(\text{stat}{)}_{-1.65}^{+2.03}(\text{syst}))\times 10^{-39}{\mathrm{cm}}^2/\text{neutron}$, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.

Figure 1

Schematic view of the proton module and the standard modules.

Figure 2

Event display of an MC CCQE event in the proton module.

Figure 3

Neutrino energy spectrum for each neutrino species at the proton module with the 250 kA horn current predicted by jnubeam.

Figure 4

Neutrino-nucleus cross sections per nucleon of carbon nucleus divided by the neutrino energy, as predicted by neut.

Figure 5

The number of reconstructed tracks from the vertex in the proton module. The colored histograms are the MC predictions divided by the neutrino type and interaction type. The neutrino interaction events in the proton module are absolutely normalized to POT, and the background events from outside are normalized to beam induced muon backgrounds.

Figure 6

The number of matched tracks between the proton module and the standard module for the two-track sample.

Figure 7

MuCL distributions for the one-track sample.

Figure 8

MuCL distributions of the first track for the two-track sample.

Figure 9

MuCL distributions of the second track for the two-track sample.

Figure 10

Definition of the coplanarity angle and the opening angle.

Figure 11

Coplanarity angle distribution following the PID cut for the two-track sample.

Figure 12

Opening angle distribution following the PID and coplanarity angle cuts for the two-track sample.

Figure 13

Event display of penetrating, stopped, and side-escaped events.

Figure 14

True neutrino energy spectra of the CCQE enhanced sample before and after applying the energy classification for the one-track sample in the MC simulation. The spectrum before the energy classification includes the side-escaped events.

Figure 15

True neutrino energy spectra of the CCQE enhanced sample before and after applying the energy classification for the two-track sample in the MC simulation. The spectrum before the energy classification includes the side-escaped events.

Figure 16

Selection efficiency of each sample as a function of the muon momentum and angle. (a) High energy one-track sample (b)  Low energy one-track sample (c) High energy two-track sample (d) Low energy two-track sample.

Figure 17

Distributions of the true kinetic energy of protons from the CCQE events in the one-track sample and the two-track sample in the MC simulation. The cutoff around 0.02 GeV stems from the effect of Pauli blocking.

Figure 18

The CCQE cross-section results with predictions by neut and genie. Our data point is placed at the flux mean energy. The vertical error bar represents the total (statistical and systematic) uncertainty, and the horizontal bar represents 68% of the flux at each side of the mean energy. The SciBooNE, MiniBooNE, NOMAD, and $\mathrm{MINER}\nu \mathrm{A}$ results are also plotted [11, 12, 13, 14].

Figure 19

Reconstructed muon angle distribution of each CCQE candidate sample. Explanations about the predictions with the spectral function model and the multinucleon interaction model will be given in Secs. 7b and 7c. (a) High energy one-track sample (b) Low energy one-track sample (c) High energy two-track sample (d)  Low energy two-track sample.

Figure 20

The CCQE cross-section results when the spectral function is used as the nuclear model.

Figure 21

The CCQE cross-section results on the assumption of the existence of the multinucleon interaction. The relativistic Fermi gas model is used as the nuclear model.