Abstract
The proton stopping behavior in proton-proton (pp) collisions at beam momentum of 20, 31, 40, 80, 158 GeV/c suggests that more physics mechanisms are at play than traditionally assumed in Monte Carlo event generators. It is shown that the thermal string fragmentation model of PYTHIA 8.303 is able to provide a good description of the observables in inelastic pp collisions such as the rapidity and transverse momentum spectra of protons, charged pions, and charged kaons at the whole CERN SPS energies.