Simulation studies of $\rm{R_{2}}(\Delta\eta, \Delta\varphi)$ and $\rm{P_{2}}(\Delta\eta, \Delta\varphi)$ correlation functions in pp collisions with the PYTHIA and HERWIG models

TL;DR

This study compares charge-independent and charge-dependent two-particle correlation functions in proton-proton collisions using PYTHIA and HERWIG models, aiming to enhance understanding of particle production and hadronization processes.

Contribution

It provides a detailed comparison of model predictions for correlation functions with experimental data, highlighting differences and potential insights into particle production mechanisms.

Findings

PYTHIA and HERWIG show similar correlation structures but with notable differences.

Correlation functions can inform models of jet fragmentation and hadronization.

Comparative analysis aids in understanding particle production in pp and heavy-ion collisions.

Abstract

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential-number correlation functions, $\rm{R_{2}}(\Delta\eta, \Delta\varphi)$, and transverse momentum ($p_{\rm T}$) correlation functions, $\rm{P_{2}}(\Delta\eta, \Delta\varphi)$, of charged particles in $\sqrt{\textit{s}}$ = 2.76 TeV pp collisions with the PYTHIA and HERWIG models. Model predictions are presented for inclusive charged hadrons ($h^\pm$), as well as pions ($\pi^\pm$), kaons (K$^\pm$), and (anti-)protons ($\rm \bar{p}$/p) in the ranges $0.2 < \textit{p}_{\rm T} \le 2.0~\rm{GeV}/\textit{c}$, $2.0 < \textit{p}_{\rm T} \le 5.0~\rm{GeV}/\textit{c}$, and $5.0 < \textit{p}_{\rm T} \le 30.0~\rm{GeV}/\textit{c}$, with full azimuthal coverage in the range $|\eta|< 1.0$. We compare the model predictions for the strength and shape of the $\rm{R_{2}}$ and $\rm{P_{2}}$ correlators as these pertain to recent measurements by the ALICE collaboration. The $\rm{R_{2}}$ and $\rm{P_{2}}$ correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively similar near-side and away-side correlation structures but feature important differences. Our analysis indicates that comparative studies of $\rm{R_{2}}$ and $\rm{P_{2}}$ correlation functions would provide valuable insight towards the understanding of particle production in pp collisions, and by extension, should also be useful in studies of heavy-ion collisions. Comparison of the $\Delta \eta$ dependence of $\rm{R_{2}}$ and $\rm{P_{2}}$ could contribute, in particular, to a better understanding and modeling of the angular ordering of particles produced by hadronization in jets, as well as a better description of jet fragmentation functions of identified species at low momentum fraction $(z)$.