Investigating late-stage particle production in pp collisions with Balance Functions

TL;DR

This paper compares charge balance functions in proton-proton collisions simulated with PYTHIA8 and EPOS4, revealing differences in particle production mechanisms and their dependence on multiplicity and particle species.

Contribution

It provides a detailed analysis of charge balance functions across models, highlighting model-dependent differences in particle production and their evolution with multiplicity.

Findings

Balance functions vary significantly between models and particle species.

Shapes and amplitudes evolve with multiplicity in both models.

Distinct differences in the evolution of width and integrals of balance functions.

Abstract

Balance functions have been regarded in the past as a method of investigating the late-stage hadronization found in the presence of a strongly-coupled medium. They are also used to constrain mechanisms of particle production in large and small collision systems. Measurements of charge balance functions for inclusive and identified particle pairs are reported as a function of charged particle multiplicity in proton--proton collisions simulated with the PYTHIA8 and the EPOS4 models. The charge balance functions of inclusive, pion, kaon, and proton pairs exhibit amplitudes and shapes that depend on particle species and differ significantly in the two models due to the different particle production mechanisms implemented in PYTHIA and EPOS. The shapes and amplitudes also evolve with multiplicity in both models. In addition, the evolution of the longitudinal rms width and that of balance functions integrals with multiplicity (and average transverse momentum) feature significant differences in the two models.