Simulation studies of ${\mathrm{R}}_2(\hat{\mathrm{I}}”\hat{\mathrm{I}}\cdot ,\hat{\mathrm{I}}”\ddot{\mathrm{I}}†)$ and ${\mathrm{P}}_2(\hat{\mathrm{I}}”\hat{\mathrm{I}}\cdot ,\hat{\mathrm{I}}”\ddot{\mathrm{I}}†)$ correlation functions in pp collisions with the PYTHIA and HERWIG models

Abstract

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential-number correlation functions, ${\mathrm{R}}_2(\hat{\mathrm{I}}”\hat{\mathrm{I}}\cdot ,\hat{\mathrm{I}}”\ddot{\mathrm{I}}†)$, and transverse momentum ($p_{\mathrm{T}}$) correlation functions, ${\mathrm{P}}_2(\hat{\mathrm{I}}”\hat{\mathrm{I}}\cdot ,\hat{\mathrm{I}}”\ddot{\mathrm{I}}†)$, of charged particles in $\sqrt{\text{s}}$ = 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 ($\ddot{I}{€}^{\pm }$), kaons (K${}^{\pm }$), and (anti-)protons ($\bar{\mathrm{p}}$/p) in the ranges $0.2<{\text{p}}_{\mathrm{T}}\le 2.0\mathrm{GeV}/\text{c}$, $2.0<{\text{p}}_{\mathrm{T}}\le 5.0\mathrm{GeV}/\text{c}$, and $5.0<{\text{p}}_{\mathrm{T}}\le 30.0\mathrm{GeV}/\text{c}$, with full azimuthal coverage in the range $|\hat{I}\cdot |<1.0$. We compare the model predictions for the strength and shape of the ${\mathrm{R}}_2$ and ${\mathrm{P}}_2$ correlators as these pertain to recent measurements by the ALICE collaboration. The ${\mathrm{R}}_2$ and ${\mathrm{P}}_2$ 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 ${\mathrm{R}}_2$ and ${\mathrm{P}}_2$ 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 $\hat{I}”\hat{I}\cdot$ dependence of ${\mathrm{R}}_2$ and ${\mathrm{P}}_2$ 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 $(z)$.

22 pages, 24 captioned figures