The NA61/SHINE collaboration measured inclusive cross sections of \pi^+ and
\pi^- meson production in the interactions of 31 GeV/c protons with carbon
nuclei at forward emission angles (0 - 420 mrad). The collaboration also
presented predictions of Monte Carlo models - FLUKA, VENUS and UrQMD, in
comparison with the data. A careful analysis shows that deviations of the FLUKA
and VENUS predictions from the data have different tendencies. The worst
description of the data was observed for the UrQMD model results.
All the models assume the creation of quark-gluon strings in the
interactions, but it is complicated to analyze the models in order to find the
source of the deviations. Thus, the quark-gluon string model - FRITIOF (FTF) -
was implemented in the GEANT4 toolkit and is used to understand the deviations
mentioned above. It was found that the most important factor influencing the
FTF calculations is the sampling of quark-gluon string masses. The other
factors/parameters are not essential for a description of the data. Also, a
good description of the data is achieved by the FTF model.Comment: 5 page