Diquark break-up jet effects on particle production in central Ar+Sc and Pb+Pb collisions at CERN SPS energies

Abstract

Abstract We investigate the rapidity spectra of protons in central Ar+Sc and Pb+Pb collisions at Conseil Européen pour la Recherche Nucléaire (CERN) super proton synchrotron (SPS) energies, utilizing the HIJING code integrated with the advanced popcorn (AP) mechanism from PYTHIA6.4. We find that the standard HIJING/AP model is inadequate for fully capturing the proton rapidity distributions observed in these collisions. To overcome this, we focus on the leading diquark (LD) break-up component, distinguishing between diquark preserving and diquark breaking (DB) behaviors. Our analysis reveals that the suppressed DB component is essential for accurately describing the proton and neutron x F spectra, particularly noting an excess of baryon number at lower x F values consistent with experimental observations. By integrating the suppressed LD break-up mechanism, informed by pp and Be+Be collision data, we successfully replicate the proton rapidity spectra and also effectively capture the rapidity spectra of negative pions and charged kaons for the studied reactions. These outcomes underscore the critical role of the suppressed LD break-up component in elucidating the mechanisms of baryon production and stopping in heavy-ion collisions at CERN SPS energies.