Pion production in high-energy neutrino reactions with nuclei

Background: A quantitative understanding of neutrino interactions with nuclei is needed for precision era neutrino long baseline experiments (MINOS, NOvA, DUNE) which all use nuclear targets. Pion production is the dominant reaction channel at the energies of these experiments.

Purpose: Investigate the influence of nuclear effects on neutrino-induced pion production cross sections and compare predictions for pion-production with available data.

Method: The Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) model is used for the description of all incoherent channels in neutrino-nucleus reactions.

Results: Differential cross sections for charged and neutral pion production for the $\mathrm{MINER}\nu \mathrm{A}$ neutrino and antineutrino flux are calculated. An estimate for the coherent cross section is obtained from a comparison of data with theoretical results for incoherent cross sections. The invariant mass ($W$) distribution of the $\mathrm{\Delta }$ resonances produced is analyzed.

Conclusions: Final state interactions affect the pion kinetic energy spectra significantly. The data for charged pion production at $\mathrm{MINER}\nu \mathrm{A}$ are compatible with the results of calculations using elementary data taken from an old Argonne National Laboratory experiment. Remaining differences for charged pion production can be attributed to coherent production; the data for antineutrino induced neutral pion production, where no coherent contribution is present, are reproduced quite well. The analysis of $W$ distributions shows that sharp cuts on experimentally reconstructed invariant masses lead to shape distortions of the true $W$ distributions for nuclear targets.

Figure 1

Kinetic energy distributions per nucleon of incoherently produced charged pions on a CH target in the $\mathrm{MINER}\nu \mathrm{A}$ neutrino flux. The solid curve gives the results obtained with the ANL cross sections as elementary input. The dashed-dotted curve gives the same distribution calculated with the BNL elementary cross sections. The data are from Ref. [40].

Figure 2

Angular distribution of incoherently produced charged pions in the $\mathrm{MINER}\nu \mathrm{A}$ experiment (data from [40]). The solid curve gives results of a calculation with the ANL input, the dash-dotted curve has been obtained with the BNL input.

Figure 3

Difference of experimental and calculated kinetic energy (top) and angular distributions (bottom). The error bars are those of the data taken from [40]. Note that in the upper figure the $T_{\pi }$ axis extends down to only 0.04 GeV.

Figure 4

Kinetic energy spectra for incoherent single charged pion production in CC reactions. The solid lines give the results for neutrino with the ANL input and a cut $W_{\mathrm{rec}}<1.4$ GeV. The dashed, uppermost line shows the single-$\pi$ production spectrum without any $W_{\mathrm{rec}}$ cut. The dotted, lowest curve shows the results for the MiniBooNE flux and a ${\mathrm{CH}}_2$ target, again without a $W_{\mathrm{rec}}$ cut.

Figure 5

Invariant mass distributions of incoherent events in which first a $\mathrm{\Delta }$ resonance was excited. The calculations were performed for a C target with the $\mathrm{MINER}\nu \mathrm{A}$ flux. Shown are the true $W$ distribution without (solid, green curve) and with (dashed, red curve) cut. Also shown is the reconstructed $W_{\mathrm{rec}}$ distribution (red dash-dotted curve) and the distributions of the $\pi N$ invariant mass $W_{\pi N}$ without (dotted green curve) and with cut (red, dot-dot-dashed curve).

Figure 6

Kinetic energy spectra for incoherent single charged pion production in CC reactions with the $\mathrm{MINERV}\nu \mathrm{A}$ antineutrino beam between 1.5 and 10 GeV. No $W_{\mathrm{rec}}$ cut has been used.

Figure 7

Angular distribution of incoherently produced charged pions in the $\mathrm{MINER}\nu \mathrm{A}$ experiment with an antineutrino beam between 1.5 and 10 GeV. No $W_{\mathrm{rec}}$ cut has been used.

Figure 8

Kinetic energy spectra of incoherently produced single ${\pi }^0$ for CC reactions on a CH target using the $\mathrm{MINERV}\nu \mathrm{A}$ neutrino and antineutrino fluxes between 1.5 and 10 GeV. The solid lines give the results for neutrino (upper, green) and for antineutrino (lower, red) beams with FSI included. The dashed lines, labeled with ‘incl’, give the corresponding results before FSI. No $W_{\mathrm{rec}}$ cut has been used.

Figure 9

Angular distribution of incoherently produced single ${\pi }^0$ in the $\mathrm{MINER}\nu \mathrm{A}$ experiment with the neutrino (green upper line) and antineutrino (red lower line) fluxes between 1.5 and 10 GeV. No $W_{\mathrm{rec}}$ cut has been used.

Figure 10

Kinetic energy spectra of incoherently produced single ${\pi }^0$ for CC reactions on a CH target using the $\mathrm{MINERV}\nu \mathrm{A}$ antineutrino flux between 1.5 and 20 GeV. Data are from [54], converted into $d\sigma /d{T}_{\pi }$.

Figure 11

Angular distribution of incoherently produced single ${\pi }^0$ in the $\mathrm{MINER}\nu \mathrm{A}$ experiment with the antineutrino flux between 1.5 and 20 GeV. Data are from [54].