Model Comparisons of Transverse Energy and Charged-Particle Multiplicity in A+A Collisions at Midrapidity from $\sqrt{s_{NN}}$ $=$ 7.7 to 200~GeV

TL;DR

This paper compares experimental measurements of transverse energy and charged-particle multiplicity in heavy-ion collisions with various simulation models across different energies and system sizes, highlighting areas needing model improvements.

Contribution

It provides a comprehensive evaluation of multiple models against experimental data, identifying specific discrepancies and guiding future model development.

Findings

Models generally capture overall trends but show deviations in low-energy and peripheral collisions.

Significant differences observed in baryon stopping and energy deposition predictions.

Highlights need for improved modeling of baryon transport mechanisms.

Abstract

We present a comprehensive comparison of PHENIX measurements of transverse energy production ($dE_T/d\eta$) and charged-particle multiplicity ($dN/d\eta$) at midrapidity to simulations from PYTHIA-8, AMPT, HIJING, and SMASH. These comparisons span both small systems (d+Au, $^3$He+Au) and large systems (Cu+Cu, Cu+Au, Au+Au, and U+U) at $\sqrt{s_{NN}}$ $\sim$ 200~GeV and Au+Au over a range of beam energies $\sqrt{s_{NN}} = 7.7$--200~GeV. Using the Rivet framework, we assess the performance of these models. While general trends are captured, significant deviations persist, particularly in low-energy and peripheral collisions, underscoring the need for improved modeling of baryon stopping and energy deposition mechanisms.