Impact of diquark models on proton, <i>π</i> ^±, and <i>K</i> ^± spectra in inelastic proton–proton collisions across 20–158 GeV/<i>c</i> beam momenta at CERN SPS

Abstract We present a systematic study of the PYTHIA 8.311 model under various hadronization mechanisms to investigate proton, charged pion, and charged kaon production in inelastic proton–proton collisions at CERN SPS energies ranging from 20 to 158 GeV/ c . Specifically, we compare four hadronization scenarios: (i) the default popcorn mechanism, which permits extended string configurations with intermediate meson formation between baryon-antibaryon pairs; (ii) a diquark scenario utilizing a QCD-based color reconnection scheme (CR1) designed to minimize string lengths, thereby restricting baryon production exclusively to baryon-antibaryon pairs; (iii) a junction-based scenario where baryon number is carried by non-perturbative QCD string junctions; and (iv) a thermal model featuring string tension fluctuations, leading to a thermal-like transverse momentum distribution. Our results indicate that the default popcorn approach inadequately describes proton stopping and hadron distributions at mid-rapidity, especially at lower collision energies. In contrast, the diquark scenario significantly enhances the accuracy of proton rapidity distributions, while the thermal model further improves the reproduction of pion spectra at lower transverse momenta and captures essential features of strangeness production, specifically suppressing K − at central rapidity ( y &lt; 1) and enhancing K + yields. Conversely, the junction-based scenario provides no substantial improvement at higher SPS energies. These findings underscore the necessity of refined hadronization descriptions for accurately modeling particle production at SPS energies.