Comparison of validation methods of simulations for final state interactions in hadron production experiments

Neutrino cross section and oscillation measurements depend critically on modeling of hadronic final state interactions (FSI). Often, this is one of the largest components of uncertainty in a measurement. This is because of the difficulty in modeling strong interactions in nuclei in a consistent quantum-mechanical framework. FSI models are most often validated using hadron-nucleus data which introduces further uncertainties. The alternative is to use transparency data where the hadron starts propagating from inside the nucleus and the probability of interaction is measured as a function of hadron energy. This work examines the relationship between the ${\pi }^{+}$ and proton total reaction cross section and transparency from a simulation viewpoint.

Figure 1

Computation of transparency (left) and reaction cross section (right) in the toy model.

Figure 2

Transparency as function of reaction cross section in the toy model.

Figure 3

Transparency for proton and ${\pi }^{+}$ for carbon with results using bare GENIE hN2018 FSI model and the toy model using GENIE reaction cross section and the $\mathrm{transparency}/{\sigma }_{\mathrm{reac}}$ ratio as explained in the text. In the GENIE simulation, all medium corrections and formation zone effects have been removed. The statistical error associated with GENIE predictions is represented with a grey band.

Figure 4

Effects of the formation zone in NEUT. The plot shows the interaction position (distance from the nucleus center) distributions of the neutrino (blue) and the starting position of the pion (green) coming from the neutrino interaction. The peak at 6 fm is at the outer edge of the Carbon nucleus in the simulation. Because of the formation zone effect, the production position of pion is shifted to the region of lower density.

Figure 5

Total reaction cross section and transparency for proton-carbon. Available data for ${\sigma }_{\mathrm{reac}}$ [22] is shown along with calculations from GENIE, NuWro, and NEUT. The transparency results are Monte Carlo, i.e., with no acceptance corrections.

Figure 6

Total reaction cross section and transparency for proton-carbon, same as Fig. 5 except for an expanded scale to show details. Available data is shown along with calculations from GENIE, NuWro, and NEUT.

Figure 7

Transparency for proton-carbon where the calculations have been corrected according to acceptance effects as determined in Ref. [27]. Available data [25, 38, 39, 40], is shown along with calculations from GENIE, NuWro, and NEUT.

Figure 8

Total reaction cross section and transparency for ${\pi }^{+}$-carbon. Available data [23] are shown along with calculations from GENIE, NuWro, and NEUT.

Figure 9

Subject of plots is same as in Fig. 5 but for the proton-argon interaction. Since there is no data available, only Monte Carlo calculations from GENIE, NuWro, and NEUT are shown.

Figure 10

Subject of plots is same as in Fig. 9 except for an expanded scale to show details. Since there is no data available, only Monte Carlo calculations from GENIE, NuWro, and NEUT are shown.

Figure 11

Total reaction cross section and transparency, same as Fig. 8 except for ${\pi }^{+}$-argon. Since there is no data available, only Monte Carlo calculations from GENIE, NuWro, and NEUT are shown.

Figure 12

Total reaction cross section and transparency for pion-carbon calculated in GENIE hN2018. This illustrates the importance of the Salcedo-Oset medium effects [19] in these quantities. “No medium corrections” means a simulation with free $\pi \text{−}\mathrm{N}$ cross sections.

Figure 13

Reaction cross section and transparency for proton-carbon in GENIE hN2018. Show dependence of Pandharipande-Pieper medium effects [26] in ${\sigma }_{\mathrm{reac}}$ and transparency.

Figure 14

Transparency for proton-carbon in NuWro. Show dependence of short-range correlation effects [27].

Figure 15

Effects with and without the formation zone in NEUT for ${\pi }^{+}$-carbon. The plot shows the pion transparency in simulations of neutrino single pion production.

Figure 16

Comparison of generator predictions of transparency for proton-carbon.

Figure 17

Comparison of generator predictions of transparency for ${\pi }^{+}$-carbon.

Figure 18

Comparison of generator predictions of transparency for ${\pi }^{+}$-carbon for kinetic energies above 1 GeV with data from Ref. [42]. Here, simulations using the NCDIS interaction without formation zone effects are shown.