Monte Carlo approach for hadron azimuthal correlations in high energy proton and nuclear collisions

TL;DR

This paper presents a Monte Carlo method to analyze hadron azimuthal correlations in high-energy proton-proton and nucleus-nucleus collisions, incorporating parton processes, energy loss, and medium effects at RHIC energies.

Contribution

It introduces a comprehensive Monte Carlo event generator that models parton production, evolution, and hadronization, including medium effects like parton energy loss in the Quark-Gluon Plasma.

Findings

Model reproduces azimuthal correlations observed in experiments.

Incorporates medium-induced modifications to fragmentation functions.

Highlights importance of low-momentum partons interacting with the medium.

Abstract

We use a Monte Carlo approach to study hadron azimuthal angular correlations in high energy proton-proton and central nucleus-nucleus collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energies at mid-rapidity. We build a hadron event generator that incorporates the production of $2\to 2$ and $2\to 3$ parton processes and their evolution into hadron states. For nucleus-nucleus collisions we include the effect of parton energy loss in the Quark-Gluon Plasma using a modified fragmentation function approach. In the presence of the medium, for the case when three partons are produced in the hard scattering, we analyze the Monte Carlo sample in parton and hadron momentum bins to reconstruct the angular correlations. We characterize this sample by the number of partons that are able to hadronize by fragmentation within the selected bins. In the nuclear environment the model allows hadronization by fragmentation only for partons with momentum above a threshold $p_T^{{\tiny{thresh}}}=2.4$ GeV. We argue that one should treat properly the effect of those partons with momentum below the threshold, since their interaction with the medium may lead to showers of low momentum hadrons along the direction of motion of the original partons as the medium becomes diluted.