Created attachment 641 [details] Multiplicity of all particles produced in p+p reaction at 158GeV/c (lab frame) In p+p reaction, simulated with G4 10.4, it was observed that elastic scattering events are wrongly marked as inelastic ones. Namely, for ~18% of events the beam proton interaction with the proton from the liquid hydrogen target is «protonInelastic», but there are only two protons in the final state and their momenta are similar to the elastic interaction. The attached histogram for the multiplicity of all particles (in 4pi acceptance without any selection) produced in p+p@158GeV/c shows the large peak at N=2, which corresponds to the reported issue.
Thanks for reporting this problem! The problem was caused by the wrong application of FTF quasi-elastic in the case of Hydrogen (A=1) target nucleus. The problem has been fixed in the development version of Geant4, and therefore it will appear in new release Geant4 10.7, scheduled for December. Moreover, the fix will be included in the next patch release of the 10.6 series, i.e. 10.6.p03 (not clear at the moment when this patch will be ready).
