Comparing the PYTHIA Monte Carlo to a two-component (soft + hard) model of hadron production in high-energy p–p collisions

Abstract

The PYTHIA Monte Carlo (PMC), first introduced more than 30 years ago, remains a popular simulation tool both for analysis of [Formula: see text]–[Formula: see text] collision dynamics and for detector design and calibration. The PMC assumes that almost all hadron production results from parton–parton scatterings described by pQCD and that multiple parton interactions (MPIs) per collision event are a common occurrence. In contrast, a two-component (soft + hard) model (TCM) of high-energy collisions, inferred inductively from a variety of data formats, attributes a majority of final-state hadrons to projectile-nucleon dissociation and a minority to minimum-bias (MB) dijet production (corresponding to measured jet spectra and fragmentation functions (FF)). The observed jet-related hadron yield is precisely proportional to the square of the nonjet yield over an interval corresponding to 100-fold increase in dijet production. The two data descriptions appear to be in conflict. This study presents a detailed comparison of the two models and their relations to a broad array of collision data. The PMC appears to disagree with some data, whereas the TCM provides an accurate and comprehensive data description.