Search for charged current coherent pion production on carbon in a few-GeV neutrino beam

The SciBooNE Collaboration has performed a search for charged current coherent pion production from muon neutrinos scattering on carbon, ${\nu }_{\mu }{}^{12}\mathrm{C}\to {\mu }^{-}{}^{12}\mathrm{C}{\pi }^{+}$, with two distinct data samples. No evidence for coherent pion production is observed. We set 90% confidence level upper limits on the cross section ratio of charged current coherent pion production to the total charged current cross section at $0.67\times {10}^{-2}$ at mean neutrino energy 1.1 GeV and $1.36\times {10}^{-2}$ at mean neutrino energy 2.2 GeV.

Figure 1

Neutrino flux prediction at the SciBooNE detector as a function of neutrino energy $E_{\nu }$, normalized per unit area, proton on target (POT), and neutrino energy bin width. The spectrum is averaged within 2.12 m from the beam center. The total flux and contributions from individual neutrino flavors are shown.

Figure 2

Cross section for ${\nu }_{\mu }{}^{12}\mathrm{C}\to {\mu }^{-}{\pi }^{+}{}^{12}\mathrm{C}$ interaction. The solid line represents the Rein and Sehgal model with lepton mass effects [8] (the default model of the signal for this analysis), the dashed line represents the Rein and Sehgal model without lepton mass effects [5], the dotted line represents the model of Kartavtsev et al. [7], and the dashed-dotted line represents the model of Alvarez-Ruso et al. [11]. The model of Singh et al. [9] gives a cross section similar to the model of Alvarez-Ruso et al.

Figure 3

Event display of a typical muon neutrino charged current single charged pion 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 and the EC indicate ADC hits for which the area of the circle is proportional to the energy deposition in that channel. Filled boxes in the MRD show ADC hits in time with the beam window.

Figure 4

Experimental performance. In the top panel, the solid line shows the history of the accumulated number of protons on target and the dashed line shows the number of protons on target passing all data quality cuts. The bottom panel shows the number of charged current candidate events in SciBar normalized to the number of protons on target. The event rate difference between neutrino and antineutrino modes can be seen clearly.

Figure 5

$dE/dx$ of muon enriched sample (left) and proton enriched sample (right).

Figure 6

MuCL of muon enriched (left) and proton enriched (right) samples.

Figure 7

Number of vertex-matched tracks for the MRD stopped sample. The MC distribution shown here is before tuning.

Figure 8

MuCL for the second track in the two-track sample. The MC distribution shown here is before tuning.

Figure 9

Maximum deposited energy in a strip around the vertex for the $\mu +\pi$ events. The MC distribution shown here is before tuning.

Figure 10

Reconstructed $Q^2$ after fitting for (a) the one track, (b) $\mu +p$, (c) $\mu +\pi$ with activity, and (d) $\mu +\pi$ without activity samples.

Figure 11

$\Delta {\theta }_p$ for the $\mu +\pi$ events in the MRD stopped sample after fitting.

Figure 12

Track angle of the pion candidate with respect to the beam direction for the $\mu +\pi$ events after the charged current quasielastic rejection after fitting.

Figure 13

Reconstructed $Q^2$ for the $\mu +\pi$ events in the MRD stopped sample after the pion track direction cut and after fitting.

Figure 14

Reconstructed $Q^2$ for the $\mu +\pi$ events in the MRD penetrated sample after the pion track direction cut after fitting.

Figure 15

Neutrino energy spectra and selection efficiencies as a function of neutrino energy for charged current coherent pion events.

Figure 16

Neutrino energy spectra and selection efficiencies as a function of neutrino energy for all charged current events.