EPOS4 Model Predictions for Global Observables in Pb-Pb Collisions at $\sqrt{s_{NN}}$ = 5.36 TeV

TL;DR

EPOS4 delivers predictions for bulk and hard-probe observables in Pb-Pb collisions at $5.36$ TeV, benchmarking against $5.02$ TeV data to assess energy dependence. The study shows EPOS4 captures the mass-dependent radial-flow signature in mean $p_T$, reproduces the charged-hadron suppression via $R_{AA}$, and indicates only modest energy evolution for these observables. The results support a consistent picture of QGP dynamics across nearby LHC energies and provide ready-made expectations for upcoming Run 3 measurements. Overall, the work reinforces the reliability of EPOS4 in describing both soft and hard sectors of heavy-ion collisions at current LHC energies.

Abstract

The study of the Quark-Gluon Plasma (QGP), a deconfined state of nuclear matter, remains a central focus of high-energy heavy-ion collision experiments. The recent operation of the Large Hadron Collider (LHC) in Run 3 at the new center-of-mass energy of $\sqrt{s_{NN}}=5.36$ TeV necessitates theoretical predictions to characterize the energy dependence and bulk properties of the medium. In this study, we present comprehensive EPOS4 model predictions for key global observables in Pb-Pb collisions at $5.36$ TeV. We focus on the centrality dependence of the charged-particle pseudorapidity density ($dN_{ch}/dη$), integrated yields ($dN/dy$), mean transverse momentum ($\langle p_{T}\rangle$) for light-flavor hadrons ($π^{\pm}, K^{\pm}, p(\bar{p})$), and the charged particle nuclear modification factor ($R_{AA}$). The EPOS4 framework successfully captures the strong mass-dependent rise of $\langle p_{T}\rangle$ with multiplicity, a definitive signature of collective radial flow. Furthermore, the predicted charged hadron $R_{AA}$ demonstrates a clear suppression, consistent with energy loss mechanisms incorporated into the model. By comparing these predictions to existing $5.02$ TeV data, we demonstrate that the EPOS4 model offers a consistent and robust description of heavy-ion dynamics, projecting minimal energy evolution for these bulk and hard-probe observables between the two energies.

Figures (3)

• Figure 1: EPOS4 predictions for (left) the charged particle pseudorapidity density for different centrality classes and (right) the charged particle multiplicity density per participant pair $\frac{2}{\langle N_{part} \rangle} \langle dN_{\text{ch}}/d\eta \rangle$ at mid-rapidity ($|\eta|$<0.5) as a function of $\langle N_{part} \rangle$, compared to ALICE ALICE_mult_ref and CMS CMS_etadist_ref measurements in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV.
• Figure 2: EPOS4 predictions for (left) $p_{\mathrm{T}}$ spectra, (middle) integrated yields (dN/dy), and (right) mean $p_{\mathrm{T}}$ for $\pi^{\pm}$, $K^{\pm}$, and $p, \overline{p}$ at $|y_{cm}|$<0.5 in Pb-Pb collisions, compared with ALICE data ALICE_ptspec_ref.
• Figure 3: EPOS4 predictions for charged hadron nuclear modification factor ($R_{AA}$) in 0-5$\%$ central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV and $|\eta|$<0.8, compared with ALICE ALICE_Raa_ref.