Unveiling hadronic resonance dynamics at LHC energies: insights from EPOS4

TL;DR

This study uses the EPOS4 model to analyze hadronic resonance production in high-energy pp and Pb-Pb collisions, revealing the effects of hadronic interactions, flow, and strangeness on particle yields and estimating the hadronic phase duration.

Contribution

It introduces a detailed analysis of resonance dynamics and hadronic phase duration using EPOS4 with UrQMD toggling, providing new insights into collision system size and multiplicity effects.

Findings

Rescattering and strangeness effects dominate at low $p_T$.

Baryon-to-meson ratios peak at intermediate $p_T$.

Hadronic phase duration increases with system size and multiplicity.

Abstract

Hadronic resonances, with lifetimes of a few fm/\textit{c}, are key tools for studying the hadronic phase in high-energy collisions. This work investigates resonance production in pp collisions at $\sqrt{s} = 13.6$ TeV and in Pb$-$Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.36$ TeV using the EPOS4 model, which can switch the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) ON and OFF, enabling the study of final-state hadronic interactions. We focus on hadronic resonances and the production of non-strange and strange hadrons, addressing effects like rescattering, regeneration, baryon-to-meson production, and strangeness enhancement, using transverse momentum ($p_\textrm{T}$) spectra and particle ratios. Rescattering and strangeness effects are important at low $p_\rm{T}$, while baryon-to-meson ratios dominate at intermediate $p_\rm{T}$. A strong mass-dependent radial flow is observed in the most central Pb$-$Pb collisions. The average $p_\rm{T}$, scaled with reduced hadron mass (mass divided by valence quarks), shows a deviation from linearity for short-lived resonances. By analyzing the yield ratios of short-lived resonances to stable hadrons in pp and Pb$-$Pb collisions, we estimate the time duration ($\tau$) of the hadronic phase as a function of average charged multiplicity. The results show that $\tau$ increases with multiplicity and system size, with a nonzero value in high-multiplicity pp collisions. Proton (p), strange ($\rm{\Lambda}$), and multi-strange ($\rm{\Xi}$, $\rm{\Omega}$) baryon production in central Pb$-$Pb collisions is influenced by strangeness enhancement and baryon-antibaryon annihilation. Comparing with LHC measurements offers insights into the dynamics of the hadronic phase.