Measurement of ${\nu }_{\mu }$ and ${\nu }_e$ Events in an Off-Axis Horn-Focused Neutrino Beam

We report the first observation of off-axis neutrino interactions in the MiniBooNE detector from the NuMI beam line at Fermilab. The MiniBooNE detector is located 745 m from the NuMI production target, at 110 mrad angle (6.3°) with respect to the NuMI beam axis. Samples of charged-current quasielastic ${\nu }_{\mu }$ and ${\nu }_e$ interactions are analyzed and found to be in agreement with expectation. This provides a direct verification of the expected pion and kaon contributions to the neutrino flux and validates the modeling of the NuMI off-axis beam.

Figure 1

Plan and elevation views of the NuMI beam line with respect to the MiniBooNE detector. The MiniBooNE detector is located 745 m from the NuMI production target, at 110 mrad (6.3°) with respect to the NuMI beam axis. The length of the NuMI target hall is 45 m; the length of the evacuated decay volume is 675 m, and the distance from the target to the MINOS Near Detector is 1040 m.

Figure 2

Comparison of the predicted NuMI off-axis and on-axis fluxes including all neutrino species. The off-axis flux is separated into contributions from charged $\pi$ and $K$ parents.

Figure 3

Reconstructed $E_{\nu }$ distribution of ${\nu }_{\mu }$ CCQE events. The band indicates the total systematic uncertainty associated with the MC prediction. The prediction is separated into contributions from kaon parents produced in the NuMI target, pion parents produced in the NuMI target, and kaon and pion parents produced in nontarget materials.

Figure 4

Mass distribution of NC ${\pi }^0$ candidates for data (points) and the MC prediction (solid histogram). The dashed histogram is the subset of predicted events with at least one true ${\pi }^0$. Predicted non-${\pi }^0$ backgrounds are either from ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ (dashed-dotted line) or ${\nu }_e$ and ${\overline{\nu }}_e$ (dotted line) interactions. Kaon parents contribute 84% of the events in this sample.

Figure 5

Reconstructed $E_{\nu }$ distribution of ${\nu }_e$ CCQE candidates. The prediction is separated into contributions from neutrino parents. The band indicates the total systematic uncertainty associated with the MC prediction. Kaon parents contribute 93% of the events in this sample.