Measurement of inclusive neutral current ${\pi }^0$ production on carbon in a few-GeV neutrino beam

The SciBooNE Collaboration reports inclusive neutral current neutral pion production by a muon neutrino beam on a polystyrene target (${\mathrm{C}}_8{\mathrm{H}}_8$). We obtain $(7.7\pm 0.5(\mathrm{stat})\pm 0.5(\mathrm{sys}))\times {10}^{-2}$ as the ratio of the neutral current neutral pion production to total charged current cross section; the mean energy of neutrinos producing detected neutral pions is 1.1 GeV. The result agrees with the Rein-Sehgal model implemented in our neutrino interaction simulation program with nuclear effects. The spectrum shape of the ${\pi }^0$ momentum and angle agree with the model. We also measure the ratio of the neutral current coherent pion production to total charged current cross section to be $(0.7\pm 0.4)\times {10}^{-2}$.

Figure 1

Event display of a typical $\mathrm{NC}{\pi }^0$ event candidate in SciBooNE data. The neutrino beam runs from left to right in this figure, encountering SciBar, the EC, and MRD, in that order. The circles on SciBar indicate analog-to-digital converter hits for which the area of the circle is proportional to the energy deposition in that channel. This event display shows the electromagnetic shower tracks from the pair conversions of the two ${\pi }^0$ decay photons.

Figure 2

Cross section versus neutrino energy of NC single ${\pi }^0$ production per nucleon on a polystyrene target (${\mathrm{C}}_8{\mathrm{H}}_8$) estimated in NEUT; the curve is based on the Rein and Sehgal model.

Figure 3

Cross sections versus neutrino energy of the total CC interaction (solid line), the NC single ${\pi }^0$ production via baryon resonances (dashed line), and the NC coherent ${\pi }^0$ production (dotted line) calculated in NEUT per nucleon on polystyrene target.

Figure 4

$\Delta t_{\max }$ distribution (4d2) after rejection of side escaping tracks. The contributions from events with decay electrons, events without decay electrons and the dirt events are shown separately for the MC simulation.

Figure 5

The minimum distance between two tracks after muon rejection cuts. The contribution from $\mathrm{NC}{\pi }^0$ production, internal backgrounds with a ${\pi }^0$ in the final state, internal background without a ${\pi }^0$ in the final state and “dirt” background events are shown separately for the MC simulation.

Figure 6

Option 1 of the EC cut: the number of track with matched EC clusters after the track disconnection cut. Events without SciBar-EC matched tracks pass the EC cut. Events with SciBar tracks matching EC clusters can pass the EC cut if they satisfy the requirement shown in Fig. 7 or Fig. 8.

Figure 7

Option 2 of the EC cut: the energy deposited in the upstream layer of the EC ($E_1$) after the track disconnection cut. Events with $E_1>150\mathrm{MeV}$ pass the EC cut. Events with $E_1<150\mathrm{MeV}$ can pass the EC cut if they satisfy the requirement shown in Fig. 8.

Figure 8

Option 3 of the EC cut: the ratio of deposited energy in the downstream over the upstream layer (R) after the track disconnection cut. Only events with $E_1<150\mathrm{MeV}$ are shown.

Figure 9

The MuCL of tracks after the EC cut. The contributions from true gamma ray, muon, and proton tracks are shown separately for the MC simulation.

Figure 10

The distribution of the number of extended tracks after the EC cut.

Figure 11

The reconstructed $z$ vertices of ${\pi }^0$s after the requirement of at least two extended tracks.

Figure 12

The reconstructed mass of ${\pi }^0$s after the reconstructed vertex position cut.

Figure 13

Expected neutrino energy spectra and selection efficiency as a function of neutrino energy for $\mathrm{NC}{\pi }^0$ events.

Figure 14

Expected neutrino energy spectra and selection efficiency as a function of neutrino energy for all CC events.

Figure 15

The reconstructed ${\pi }^0$ momentum after all event selection cuts.

Figure 16

Cosine of the reconstructed ${\pi }^0$ angle with respect to the beam direction after all event selection cuts.

Figure 17

The true ${\pi }^0$ momentum of generated MC events (solid) and selected MC events (dashed) for all $\mathrm{NC}{\pi }^0$ production processes (top), and the true ${\pi }^0$ momentum dependence of the efficiency of $\mathrm{NC}{\pi }^0$ production (bottom).

Figure 18

The true ${\pi }^0$ angle with respect to the beam direction for generated MC events (solid) and selected MC events (dashed) for $\mathrm{NC}{\pi }^0$ production (top), and the efficiency for $\mathrm{NC}{\pi }^0$ production as a function of the true ${\pi }^0$ direction (bottom).

Figure 19

The true ${\pi }^0$ momentum ($P^{\mathrm{true}}$) versus reconstructed ${\pi }^0$ momentum ($P^{\mathrm{rec}}$) from the MC simulation. The solid line shows the identity.

Figure 20

The true ${\pi }^0$ direction ($\cos {\theta }^{\mathrm{true}}$) versus reconstructed ${\pi }^0$ direction ($\cos {\theta }^{\mathrm{rec}}$) from the MC simulation. The solid line shows the identity.

Figure 21

The ${\pi }^0$ momentum distribution after all corrections described in the text, with statistical (error bars) and systematic (red boxes) uncertainties. The dashed line shows the Monte Carlo expectation based on the Rein and Sehgal model.

Figure 22

The ${\pi }^0$ angular distribution after all corrections described in the text, with statistical (error bars) and systematic (red boxes) uncertainties. The dashed line shows the Monte Carlo expectation based on the Rein and Sehgal model.

Figure 23

$E_{{\pi }^0}^{\mathrm{rec}}(1-\cos {\theta }^{\mathrm{rec}})$ after fitting. The coherent contribution and other $\mathrm{NC}{\pi }^0$ are separately shown for the MC simulation.